Crosstraining

I have been using step aerobics as my primary cross training activity for about 3 years now. I have been listening to podcasters who use other activities as their secondary activity, such as biking and swimming. I'm not interested in using swimming as a secondary activity, that tends to bulk up the upper body and I'm naturally bulky anyway. However, I do have a bike. I just need to get it fixed, new tires and possibly a new chain. I would need to find a local trail where I could ride without getting hit by cars. I haven't ridden a bike in 12 years, I wonder if what they say is true, that you never forget how. I also wonder how much it would cost to get it fixed. This warrents investigation.