Some people pick up the basics in a few hours. Having some good instruction, good location, good wind and good kite helps. 8-) (I had none and still did the first few reaches my second day out) After that you won't progress easily with a surf board and you may not realize how much it is limiting you in getting better.
Bigger is easier to get the basics down. I would go for a smaller board however. It'll take a little longer to get the hang of it but you won't outgrow it anytime soon.
Check out
www.jimmylewis.com. Dwight (who posts here too) seems to like his a lot. Other companies you can search for are Naish, Fanatic, AHD, RRD, Litewave Designs, Roberts, Twintip, Airrush, Slingshot.....and gobs of custom builders. You should find specs on the websites of the above brands.