I'm really impressed with how friendly everyone on this board is, so I was hoping you could provide me with some guidance.

I won't even call myself a newbie, since I don't own a bike yet (well, haven't in the last 10 years anyway). Here's my situation:
The guy I'm seeing lives for riding, racing, etc. and would really like me to get a bike too so that I can join him once in a while. I would like to, but don't have much money to sink into it. I feel like he would like me to spend more than I want to, since he is into high-end bikes, so I thought I would ask for your advice, and see if I'm being realistic or not.

First off, I'd like to keep the cost around or under $250. Are there any bikes in that price range that will not fall apart with normal wear and tear? I intend to ride on bike trails through state parks, paved trails and roads. No hopping, stairs, or any other form of "rough" riding. Do I need front suspension?

Also, I'm pretty short (5' even), so I need a bike that's 14" or less. This has narrowed my choices tremendously. Stores do not usually stock bikes that small, so I can't just test them out and see what feels best. I've also read that being short/small makes for really rough rides on aluminum frames. Is this true?

Anyway, the bikes I've narrowed it down to are these:

Diamondback Sorrento
Trek 800 or 820
Giant Boulder
Trek 3500
Gary Fisher Tarpon

I would welcome anyone's opinions, insights or ideas on alternatives. Thank you all so much for your help!