sorry, cant answer about the biking, but i thought i would answer on the single sceen. as far as i know from living a few places and from friends that have moved around, Boise is pretty good in that area. There are night clubs, etc, but there are also lots of fun festivals in the park, and nice themed parks to meet people at/in. There are definitely singles here, many many college age obviosly, and many older, and much older too. Boise seems to attract all people, whether it be the outdoors, the college or the relativel cultured lifestyle for the size :)
As far as apartments, they do turn over most when school starts and stops, but there are nice places available most all of the time, as Boise is always growing, and always building. If you are looking for at a house right now, though, its pretty bad, things here are really overpriced at the moment, but i hear that we arent the only ones. so you might want to wait on that market.
well, good luck with everything! maybe we'll be seein you on the greenbelt (which is awesome btw, i rode it all the time for miles and miles when i was in college, and now i frequent it to swim at one of the lakes along it :)
~Stephanie