There actually aren't too many breaks....and you will almost definately need to hire a car (or 'moke' - which is cheaper) to get around. July is not the best time to surf in Barbados either!....much better Nov-April, but you might get lucky. I learnt to surf in Barbados on the south coast (the west coast is on the Caribbean side and protected from the wind/swell so usually flat)....you should try 'Freights' and/or 'Southpoint', the fomer a nice mellow left/point break (kids and beginners) and the latter a reef break. Also try 'Brandons' on the south coast (opposite the garrison savannah), it's a reef break, but again, usually small and easy to walk out.
If you want bigger you should check out the east coast which is on the Atlantic side - so usually gets bigger waves all year round. 'Bathsheba (the soup bowl)' is the main place, and on the right 50yards away is 'Parlors', which can hold much larger waves, but is perhaps easier to surf than Soupbowl as the takeoff is easier. Otherwise try 'Duppies' if you feel brave.
All in all - warm weather and super warm water.....and the reefs aren't too bad - you can always wear booties!
If you get stuck ask for a guy called 'Zophor Taylor' (super friendly) or the guys from 'Dead or Dredd' surf shop (next to Fred's bar) - both are on the south coast - super friendly and will rent you a board and/or give you the chat.
Hope this helps!