Out of all the major cities in the U.S. Los Angeles has some of the most diverse topography (Mountains & Hills) that separate many areas of the city and surrounding areas. As a result our tower based mobile systems form a tale of 4 Networks, and not one is perfect. In general it really depends how close you live and work to the nearest tower. Verizon seems to have the best overall coverage and seems its CDMA technology tends to work very well even penetrating the depths of most buildings and parking structures. ATT is a GSM 3G network in most parts of L.A. and is about equal in speed to Verizon, however, especially if you are on an iPhone it tends to drop more calls than any Nokia's that I've owned in the past and used on the ATTA network. (Handsets also play a factor in reception. T-Mobile also (GSM) gives you the best deals on minutes and their customer service is Outstanding, however their Network its 3G and Edge Networks is spotty compared to Verizon and ATT's networks. Sprint like Verizon is on a CDMA network as well although their Networks footprint for high speed data is the smallest out of the four even if it can clock some of the fastest data speeds.

Above all he most important thing to consider when choosing a cell phone provider is whether there is good coverage in the areas you use your phone the most. Here are some ways to check coverage before you sign a contract.

1. All of the major carriers offer coverage maps where you can put in an address, intersection, ZIP code or city and see the strength of the coverage.

For T-Mobile, go to t-mobile.com/coverage; for Sprint, go to sprint.com/coverage; for Verizon Wireless, go to verizonwireless.com/b2c/CoverageLocatorController; For AT&T, go to wireless.att.com/coverageviewer.

2. When you go to one of these Web sites, first enter you home address to check the coverage around your house. You might want to also enter your work address, a relative or friend's address, or anywhere else you plan to make a lot of cell phone calls.

3. If you are thinking of getting a data plan with your phone so you can surf the Web or send and receive e-mails, check the maps to see the strength of the data coverage.

4. If you want to compare all of the carriers at the same time, you can use Signal Map (signalmap.com), which relies on user submissions to display signal strength. The site is only as good as the information people submit, so don't rely on it exclusively.

5. If you are still worried that you won't get reception in your neighborhood, ask your neighbors what cell phone carriers they have and whether they get good reception. You should also inquire about how long you have to return the phone and cancel your contract if you don't get service in your house.

Here's a cool Gizmodo article that shows averages among many cities across the country (LA isn't one of the cities, though) - http://gizmodo.com/5111989/the-definitive-coast+to+coast-3g-data-test

I'm going to have to choose Verizon Wireless. I'm from Oakland and I went to live to LA for 5 months and I never had a problem with their service. To be honest I have never had a problem with Verizon anywhere. I do believe they have the best service. If you decide not to chose Verizon, DO NOT choose T-Mobile. T-Mobile may have the best phones from all other companies, but their service sucks. Gudluck though!

Unfortunately they did not include LA but Gizmodo did a comprehensive 8 market review of the 3G offerings from AT&T, Sprint, T-Mobile, and Verizon. Their results were very interesting.

As many of the other people responded, network speed is usually a result of the combination of many factors.

EV-DO and HSPA are probably going to give you potentially the fastest air link interface but things like coverage, antenna diversity, carrier frequency, handset software, sector saturation, and back haul from the towers all play a major role in how fast your connection goes.

Edge will never get speeds anywhere near what EV-DO and HSPA can deliver, but then again if all you have is edge coverage where you are, then i am guessing it will go faster. :)

AT&T/Verizon overall (depending on location in LA), Sprint, then T-Mobile. T-Mobile's high speed footprint is too small and Sprint's coverage isn't what it was from 2 years ago when they were first in the game for high speed access. For me, 3G speed is only one part of the equation. The other factors include: coverage (domestic AND international), device diversity and device functionality. (WiFi, etc).

Verizon is the fastest! From experience, I've used a Verizon wireless card in both New York City and Los Angeles, and it works fine in both places!

In the Los Angeles area, Sprint and Verizon are the fastest, reliable networks with the best overall coverage. In my experience, both are really close to each other in all areas of testing. In experiments we did at the So Cal Wireless Users Group, a couple years ago, we did a head to head with Sprint and Verizon. Sprint had slightly faster download, Verizon had slightly faster upload. I personally use Verizon EVDO Rev A. all over So Cal in my car and it's always fast and usable.

Your Blackberry isn't supposed to be faster on EDGE based on pure bandwidth. You might be seeing some of the Blackberry optimizations that don't occur on the iPhone 3G. Like scaled down websites and optimized email. I'm not sure but Blackberry might even be compressing the bitstream behind the scenes - like Verizon did with Venturi software.

ATT's network is still being built-out in LA so it can be overwhelmed. But, the iPhone also has a lot going on in the background. Your experience with slow network activity could be from your power-user, uh, usage. Try powering off and on to reset the iPhone every day or so. That's what I do when I notice it getting slow.