I had a quick look on a website called "vrbo" it used to be homeaway holidays, and a quick search for 4 weeks you're looking at 400€ upwards,i think this is your best bet as it counts as a holiday so no deposit,and obviously the electric etc is in with the price , you can narrow down your search as to where you'd like to be and if you'd like wifi etc.As Graham c pointed out its getting quite there now so maybe look for a place in the centre of santa pola, if you need anymore help or advice please ask, we're not out there at the but arw in hand if you need us.
Regards
Dave