When wanting to tour the Magic Kingdom Monorail Resorts my suggestion is to park at the TTC and from there take the Resort Monorail to each of them, if you would not be doing this after going to the Magic Kingdom. Last month when my parents and I stayed at the Contemporary I saw a lot of cars from our Magic Kingdom view being turned away from parking at the Contemporary, during all hours of the day. Maybe it had to do with the fact that a huge Gospel singing group was staying there, however I am sure you would not want to be told that you need to turn around and leave.
I can't speak for how strict they are for parking to look around the Polynesian and Grand Floridian, however I am sure there are times when they have been as strict as the Contemporary. So I say again the best thing to do if you want to look at the Magic Kingdom Monorail Resorts if you're not coming from the Magic Kingdom, is to park you're car at the TTC.