Interesting Topic . If you want to ride in mountain area you need a bikes that perfect for downhill and uphill riding. You know there are 10 type of mountain biking . So you have to choose a perfect bicycle that give benefit to ride in all type . You can read this for getting a perfect bike http://www.bikejar.com/best-mountain-bikes-under-500/
I hope you will be able to choice a perfect bicycle for your new adventure . Happy MTB riding .