i wrote here in december looking for some suggestions on a bike for my first commuting bike (new at this, any recommendations for a bike?) so i wanted to give a quick update on what i ended up with! i first wound up with a gary fisher solstice. it wasn't exactly what i wanted, but it was free and comfortable. so i rode it in san francisco for all of 2 weeks before lugging that heavy thing up 2 flights of stairs finally got to me and i left it locked up to a pole in front of my apartment overnight and it was stolen. i was without a bike for nearly a month and at the whim of public transportation (keep in mind i ride the cal train from san francisco to san jose 3 days a week) during that time. i was looking around on craigslist and at the LBS's around town for another bike, and i was also sized at a 48cm frame.
i decided that my next bike was going to be much lighter, even at the expense of just about everything else. i have to carry it up stairs (up 5 flights of stairs twice a week, up 2 flights every day) and onto the cal train nearly everyday. it had to be light. well, finding a reasonably priced bike, in reasonably good repair in that frame size is like a needle in a haystack!! it was ridiculous. but i finally found a pretty good bike--a bianchi eros. its about 10 yrs old and i paid $100 for it. i guess patience pays off. in all, the frame is in fair condition with some scratches and whatnot, but i still think i got a pretty good deal. yay for me!
i just wanted to say thanks to everyone for being helpful and answering my noob questions with patience. in the end, i probably could have kept looking and i think the eros is a great bike but probably not perfectly suited for my needs. its still a sweet ride and even with all of the scuffs from being 10 years old, i still get plenty of compliments and drools over it from friends and strangers. needing such a small frame size really made my search difficult and even in the bike shops my options were very limited. i will try to get a picture up so you can see it. just wanted to say thanks!