You are staying in town so you are limited in your choices to those who will pick you up in town, or those who will pay your cab fare to the caleta. Unless you want to take your own taxi to the caleta each day (which will run you about $20 return) or you rent a car.
Those who pick up in town are Aqua Safari, just steps from your hotel, and at the pier further down the road, Living Underwater, Aldora, Blue XTSea and, I think, Deep Blue. There may be one or two others but they escape me at the moment. Dive Paradise operates out of the Barracuda Hotel which is down a block or two the other direction. I have heard others on the board say that Tres Pelicanos and Blue Magic will pay your cab fare to the harbour, but you would need to confirm that. As to 4 dives a day, I rather suspect that will be difficult to line up. First of all, due to the depths of most dives (and especially dive time lengths with the steel tank operators), it is hard to get them all in during daylight with sufficiently long surface intervals in between. As Don mentioned, you are coming at a VERY busy time...highest of high season, pretty much. Good luck finding someone!