I'd err on the side of caution. Definitely take a friend, and inform people of where you're going. Have your parents drop you off so that one of them can at least meet this person and let it be known in a subtle way that they're aware of where there son is. It'd be a good idea to have a cell phone with you or a way that you can call your parents to assure them you're ok. (or they can call you if they don't hear from you in a reasonable amount of time)

99% of the time, you're probably going to be fine. However, there's always that 1% of idiots who want nothing more than to start up some kind of relationship with an inexperienced teen.
Trust your gut. If something feels out of wack, get the hell outa there asap.

Even after a long period of time goes by, an experienced predator can trick you into a false sense of security.
ie, you've been going over there for 6 months and feel real comfortable.. hey, maybe the guy even lets you drink a few beers or whatever..
He invites you over one weekend while his wife's away. Offers you a drink.
Next thing you know it's 8 hours later and you have no idea what happened.
(he spiked your drink with GHB and has been playing around with you for several hours while you're passed out)

Just be real careful and always make arrangements to call somebody by a specific time. If they don't hear from you...it's time to wonder what's going on and find out where you are and what you're doing.