Hi mmhernan,
I'm new to cycling too and have also decided to do a nearby MS ride!

I just bought a Specialized Crossroads hybrid for $360 and so far am really enjoying it. My advice is to be clear about what you will be using the bike for when you talk to the folks in the bike shop (my requirements were for a beginner cycler using road and light trail, carrying a few things about) and visit a few shops if possible. Ask as many questions as you can and try the bikes out.

I'd also advise you to budget in some money for the additional bits that you will need or want for cycling - helmet, lights, lock, water bottle & cage, cycling shorts, panniers, bike rack, computer, gloves, etc. I hadn't really considered this aspect when I bought the bike and am finding that the cost of these other items is steadily accumulating!

Anyway - hope that's helpful. Let us know how you get on - good luck!