padi & cmas have an agreement on various levels, the entry level is just paperwork, for the rest it's like additional training... therefore not really interesting for you.
Just find a PADI dive center (
www.padi.com) in the region and give it a shoot. I would say that the one in carry is pretty well known (haven't tried it). For the wrecks, there are loads down there, but don't be surprised if they ask you do to a check dive, at 6m for mask clearing etc... that's somewhat a procedure down there.
don't forget the medical as some stated... it's compulsory by law, therefore if you don't have it... you don't dive.
For the rest, don't be surprised either to see autonomous divers go down to 210 Ft on Air... that's quite a change from the PADI way of diving...
Loads of the wrecks are deep down there, but some of the sites are wonderful, i hope you'll get some nice dives and give us a good feedback on the area.
The licence is certainly not compulsory... don't let them buy you into that... it's just if you go in the "club" like an association that you have to do so. If you provide your DAN or other V&B insurance which is valid, you can dive without the club fee, there is no legal obligation to do so... just get into the real commercial dive center and not the "club" which normally by law should be restricted to "club participants" and not "people who come and go".
Enjoy your stay