When we signed up, we were given an affinity card and a randomly-selected initial free play credit. You can use the free-play credit at most of the slot machines, although you do have to put in a little bit of money to "prime the pump." Now it's possible to game the system so that you end up being able to take away most or all of the "free" money, although in our case we were enjoying ourselves too much playing the game and we frittered it all away, but in the meantime we were earning the two types of points the program accumulates. I still don't completely understand how the points accumulate, but somehow we managed to accumulate the required 20 "tier points" in the first 24 hours after signing up. (I think we probably were out about $50-$60 in slots, keno, and tracked blackjack table play, although of course the total amount wagered was more since we won some and lost some along the way.) That got us one free breakfast/lunch buffet at Toucan Charlie's, worth between $12-$20. It's unlikely that any of us are sufficient high rollers to get up to even the first bonus tier (Preferred) of the program during such a short stay, but it still seems like it's worthwhile to sign up if you're planing on doing any gaming at all; just remember to cash out whatever comps you've earned by the end of your trip unless you're expecting to be back within a year, since you'll forfeit the points if you don't earn some at least annually.
If you don't plan on gambling, you can just skirt the edges of the casino while you come and go to your hotel room and the restaurants.