You most definitely don't need seperate bikes for riding around the neighbourhood and riding bike trails (assuming these aren't mountain biking trails). If they aren't, then a lower end or medium priced road bike should do the trick. Unless your planning on real major rides or races, you won't need a super high-end one. And if they are mountain bike trails, you can ride around town on a mountain bike, just your speed will be limited somewhat. Personally, I'd suggest staying away from hybrids, as in my experience, they just tend to not be great bikes. When you're buying, find a good bike shop. Don't buy from Wal-Mart or the like, they're craps bikes built in craps ways. A local bike shop or co-op will help you find just the right bike at just the right size and with just the right amenities. And some will even have programa to get it at just the right price.