I've seen people riding those Walmart Mongoose full suspension bikes on paved rail trails. Not my first choice of a bike on pavement, of coure they didn't even know what height to put the seat at - legs bent out at funny angles and all. I guess Walmart didn't fit them properly.
I've get a Gary Fisher Tassajara (hardtail) and it's held up very well. I've looked at the Specialized Rockhopper for my son and it looks like a decent bike as well. I think you would do well with either brand. I don't know anything about Marin's - have only seen them in a store once.
Remember, if you buy at a good lbs, they'll stand behind their product and help you as you learn.
Mark