If you are already booked at Ramon's why not dive with them too. They are as qualified as any other place. As everyone who reads this board knows, I always promote Ched. However, since you are newly certified, will be staying right there and can spend some time hanging out at the dive shop, I suggest you seriously consider doing this.
You can learn a lot this way, they can learn a lot about you and after each dive/day, adjustments can be made.
I know you will be back to San Pedro for more diving (it's kind of addicting). So use this trip as a base, walk around, get to know people but don't worry about getting the best "DEAL" on this trip.
One last tip: I would urge you to not go off on your own, follow the dive master. S/he will show you the best there is where you are.
HOWEVER, follow does not mean "CLING" The biggest mistake new divers make (and I did too) is staying to bunched up, kicking each other, stirring up the bottom, etc. Ten to 20 feet to one side or behind is still following.
Take only pictures leave only bubbles