Yeah, diet in the offseason when you are still working on building basic endurance and strength. Also, eat plenty of food on the bike, pay attention to carbs pre-ride and carbs/protein post-ride, and then for everything else you can watch your calories. When I'm doing these long training rides, I have a hard time not dropping too much weight and losing strength/power. Just keep riding the bike, and you'll be fine.

When the spring rolls around and you want to really kick up your speed, ride with people faster than you (but not THAT much faster). Be prepared to get back by yourself potentially (depending on your group) and to swallow your pride. Really, you'll push yourself well beyond your comfort level. I rode with some new groups this summer that cruised at speeds that used to be my "sprints"! I had to learn to sit in and keep up. It was so hard, but I learned a lot and improved more than I had in months of riding with people of the same fitness and experience levels.

Racing is fun, and really collegiate teams are full of people of all sorts of skill levels. There are a bunch of categories for collegiate racing, though only 2 for women. Still, the women's Bs are a great place to start (better than the regular Cat4 IMO). When you join the team, talk to your teammates and pick their brains about racing and training. Don't worry so much about turning yourself into a "racer" before you join the team. Just keep plugging away at your fitness goals, find some nice people to ride with who will challenge you, and have fun!