Hi there!
I came from Guadeloupe less than 2 weeks ago! I had my own board with me and my level is intermediate, but I decided to take lessons anyway. I had chosen the instructor from searching on the web, but it turned out to be the perfect choice: http://www.guadeloupe-karibik.com
It's not a camp like it says, but instead you meet up with the instructor. He's an easygoing guy with a lot of patience, and also sincere in his work. He will get you standing on your first lesson

I saw a couple of other instructors, but this one I can highly recommend!
Guadeloupe is very difficult to stay on, if you don't have a car. It means you're stuck in one place, since there are no public transportation, and the taxis are expensive. You would have to (like you say), stay close to where you can walk to a beach. All the waves (as far as I know), are on reef. It means you have to paddle far out, and not ride the wave too close to the beach, because it gets shallow.
Many beginners surfed at Helleux beach (in French plage du Helleux), and there you don't need to paddle far out. It's not far from the small village Sainte-Anne. The beach itself isn't very nice, so you would go there to surf mainly. If you search on the web, and since you are a group of people, you can easily rent very affordable bungalows or apartments very close to this beach.
(In regards for the tips of spots on wannasurf.com, I'm surprised to read that Port Louis should be sand. I was there, and it was definately on reef when you paddled out. About going to Martinique, I wanted to go there too to surf. I did end up there, but never surfed, and from what I heard from people on Guadeloupe, the surf was not such a big thing there.)
For me as a single traveler, it would quickly get expensive, and just too much money for me to rent a car. I'm planning on going back again in 2 weeks time, and have been searching for accomodation in walking distance from two beaches with surf, I'm now familiar with
I hope this was somehow helpful. I felt totally "blind" before I went there, only having the web to trust, so I completely understand you.