Sata2 = 3gb/s, Sata3 = 6Gb/s.
Yes, SSD's are better served from a sata3 port, 6Gb/s.
Yes, a single 7200rpm sata3 (6gb/s) drive will perform just as well on a sata 2 port as it will on a sata 3 port, so yes, a sata2 drive will perform almost identical as a sata3 drive in real world performance. You will only see a difference in synthetic benchmarks.