My associate Comm-Lead (aka http://curikim.com) and I performed a FRS radio check on our way home from downtown. We used store bought 12 (14?) channel Motorola talk-about FRS radios. We took two different routes from work to home, here’s a map:

View FRS Test Route in a larger map
The map is somewhat self explanatory, but here’s some notes. We had very good coverage until Curi hit Duboce and Market. At that point I could pick her up if I turned the squelch all the way down. For the remainder of the trip I could tell there was a background signal but I could not make her out out until she reached the hill on 17th and Clayton at which point I was at Masonic and Fell and received an excellent signal.
It seems from our test that in a flat part of the city, the expected range of FRS is about 4-6 blocks.