I dive in Gran Canaria several times a year as I have a timeshare near Puerto Rico (well I have to spend my profits from YD somewhere!!!).
I dive with
Scubasur Dive Centre and the diving is superb. I have posted a dive report
Here - they have just taken over another diver centre in Puerto Rico called
Top Diving.
If you plan to go to Gran Canaria, then you won't go wrong with either.
Regards