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.
Most of the trails that I've been looking into here are asphalt, some say dirt/grass/gravel. I don't believe they're really mountain biking trails but I would stick with the beginner trails anyway for now. Do you think a road bike would be good for my purposes? There's a bike shop close to me that I went into about a month ago to look and get a good idea on what I wanted, but they were adamant on selling me some $800 bike that I probably didn't need. I don't really have $800 to blow right now, and I'm not too sure that's the going rate for what I need... There's so much conflicting information, I guess because it's mostly a matter of opinion, on what brands are best and all of that. Thanks for your reply!
Do not spend $800 on a bike you aren't sure about. I'd say find a different bike shop if you can, you should be able to find a perfectly good bike for you for less than $250. Check for used bike stores, as these will be cheaper, and will likely be willing to help customize the bike some too. And yeah, go with either a road bike or a touring bike, if you want to use it for grocery runs and the like.