This is a controversial question, but according to rootmetrics's results AT&T and T-Mobile provide a very good performance in the San Francisco area ahead of Verizon, while Sprint is lagging pretty far behind.

In detail:

• Call Performance: no major differences between AT&T, T-Mobile, Verizon, Sprint
• Data Performance: AT&T, T-Mobile, Verizon strong, only Sprint is lagging far behind
• Text Performance: no major differences, again Sprint slightly behind
• Combined Performance: AT&T, T-Mobile, Verizon strong, only Sprint lagging far behind

More:

• RootMetrics Coverage Map San Francisco
• Sensorly Coverage Maps
• RootScore Report San Francisco Bay Area
• PCMag -  Fastest Mobile Networks 2013

See also the following post:
Where to get a mobile phone/cell phone and how much is it?


Image by Sebastiaan ter Burg via Flickr

• In the US you usually have to pay to make calls, but also to receive calls (same for text messages). One of the reasons is that there are no dedicated mobile phone numbers. So callers cannot determine by the number, if they are calling a landline or a mobile phone. When you get your phone contract you will most likely be able to choose a number from your local region (e.g. '650' for most of the Bay Area)
• Compare the coverage of the available carriers on RootMetrics 
• To keep costs low in the beginning, I got a no-contract, pay-as-you-go offer from BestBuy, called 'H2O Wireless pay-as-you-go' without monthly fees and pretty low rates (10 USD for 200 minutes, 5 cents per minute/message and 10 cents per MB)
• Ting offers even lower rates, but I have not tried it myself
• By using Apple Facetime, Skype and other VoIP-Apps (explained here), when at home or elsewhere with WiFi connection, we were able to keep the monthly bill at around 20 USD/month 

See also the following post:
What is the best mobile provider in the Bay Area and San Francisco?

(note: no guarantee that the below hints work, try it at your own risk)

• Check the type label on your device, if it supports 100-240 Volts and 50-60 Hertz, if so it should work using a plug adapter, e.g. for Europe to US
• Most devices involving engines and heaters (e.g. hair dryers, toasters, drills, vacuum cleaners) won't work with the lower voltage and that's why we bought them in the US
• If it's a device that is not supposed to work with the above values, a power converter would be required. For my German TV (only supporting 230 Volts) I got this converter from Goldsource and it works like a charm
• But although my TV has a built-in digital receiver, I had to get an external receiver to be able to use the antenna's signal, as it's based on a different system

• Get a good antenna and a receiver (e.g. European systems seem to be incompatible):
• Mohu Leaf Paper-Thin Indoor HDTV Antenna - review
• C2 ClearStream Antenna - review
• Check your TV Signal: TV Fool Choisser Channel List 
• Or get Aereo in case legalized and as soon as it is available in the Bay Area
• Watch via app or web:
• Hulu (free)
• The CW (free)
• Netflix (7.99 USD/month

The US' TV and telecommunication market is known for its high monthly costs compared to other countries and it comes with a huge variety of combined offers which can leave the freshly moved geek simply confused. 

E.g. often 24 month contracts are offered for a relatively low monthly payment, which increased after 3 months and again after 12 months - both only mentioned in tiny letters below the main offer - or only in combination with expensive channel packages.

To keep the costs low in the beginning I did the following:

• Getting the cheapest Internet-only connection (calculated over the whole 24 month period, to be able to compare the overall costs - in our case the cheapest was Comcast)
• Get TV over the air (see here) and via apps
• No phone landline
• US Calls: use mobile phone
• International Calls: use Voice over IP (in my case with a free German number from sipgate using the app Groundwire)

Image by Thomas Leuthard via Flickr