I agree on the someplace warm from not just a nice to be out of the winter idea, but also from an ability to get in more flying time. I have not heard any bad things about the 3 day courses, but I believe to be really proficient it takes longer than that. I took about a month to get my multi in my Baron, flying 2 - 3 times per week. I ended up with about 27 hrs before taking my checkride.
I see advertised 7 to 10 hours and not that you couldn't do it, I'm just not sure I would have been comfortable with that few of hours. While you could learn what it takes to pass the check ride, I wanted more time to be truly proficient. The nice part is that since many insurance companies want several hours of dual or charge a ton, my insurance company didn't require anything and my rate was reasonable (although I did have 700 hrs retract before owning the Baron).