"My name is Jeff, and I'm calling you because you've stayed at one of our resorts in the past, and you qualify to win an all-expense paid trip to the Bahamas.."  I don't know if it's really a scam, but I haven't heard of a pitch that starts out like that which wasn't one. Next time they call, I'll interrupt the pitch and demand exact details on which "resort" I've stayed at. Exact location, dates.

I'll note that this is the second time I've gotten a call from them that starts with 510-604-xxxx (the area code and prefix of my phone). I suspect that they're trying to use numbers that look as local as possible to get people to answer.