Hiya,
I've been going to Tenerife for over 25 years and at the beginning I was really young and learnt the language in about 2 years by going 4 times a year. Then I spent a year learning Spanish law at the University and found that my language in that 12 months really improved beyond anything I learnt in England. Being in the country really did help - it does give you some bad habits as the Canarian accent is not as strict as the Castillian accent, but definitely being in the country helps loads