Brakes are usually the last thing you need on pavement or small trails so I don't think you should look past a good bike with non-discs. I'd choose a good, used bike over a new bike in your case given your budget. Ebay always has used bikes for sale so keep an eye out for ads posted within your area so you can test ride the bike that fits your budget and needs. There is a bike shop in my area that specializes in used, reconditioned bikes. See if there is one in your area because there may be some good deals out there to be had.

My '89 Mongoose IBOC Comp is a really nice bike that I still enjoy riding. Don't overlook an older bike in good working order.