I used them about 11 years ago in an attempt to complete my PPL(A) training. The experience was not a good one - at that time.
I had pre-booked 4 hours per day for two weeks. On arrival the British Instructor was just leaving for two weeks holiday and the remaining instructor had far too many students requiring training. I had occasions where pilots were taken up in the rear on the plane so that they didn't feel they were being abandoned.
In the middle of the period there was a strike by the fuellers and trips to Seville were needed to refuel the aircraft.
You need a security pass to access the apron and that takes several days, and when you get it it doesn't work properly.
There are also some interesting differences in flying practice in Spain. For example they don't use QFE so you need to know airport elevation and adjust the QNH. Every flight out if Jerrez requires a flight plan to be faxed to both ATC and Security with a departure time. You have a 30 minute slot - miss it and you have to file another plan.
I did not get my training as booked and I did not complete my PPL. Returned to the UK and completed it here.