I suggest that you visit Koh Tao, a small island in the Gulf of Thailand. It is a fantastic place for a diving/snorkel holiday.
Since you will be "buddy-less" (wish I could join you!) Koh Tao is the ideal place to go to since many young people from all over the world go there for a diving vacation. You would not be "buddy-less" for long.
There are also many reputable PADI dive centres on the island through which you can do your rescue course.
I have been to Koh Tao on two occasions in the past and can provide you with lots of info if you wish. See my photos for some pics of Koh Tao.