I would suggest the rental market in South Costa Blanca has reached a level at which you will have to work very hard to ensure you get an income. There seems to be a huge amount of places to rent wherever you look and, most people I have spoken to, are lucky to rent out for 20 weeks out of the year regardless of location. There are, quite frankly, just too many properties on the market so you really need something that makes it stand out (fab website, right on the beach, in the middle of a golf course etc). My flat, which I don't rent out, is in the middle of three golf courses and is a 10 minute drive to the beach plus has great restaurants and nightlife and the obligatory swimming pools. However, our street only has 4 permanent residents which means 15 duplexes and 12 villas available for rent. Even in high season, only about 3 or 4 of them are rented out for longer than 3 or 4 weeks.
Almeria is a newer area which hasn't been fully exploited yet so the chances of renting may be better but, last time I drove through, the amount of building probably means the same situation you now have on the Costa Blanca.
And, to throw a spanner in the works, I've been reading that the powers that be are clamping down on "unlicenced" rentals. Apparently you have to apply for a licence to rent out your property and ensure all building codes, safety features etc are being complied with before a certificate is issued. You also have to have permission from your urbanisation committee if you live on one. Fines of up to 20.000 euros have been imposed on renters without licences and, of course, any rental income will be subjected to tax. Costa Blanca News (to be found on-line) has reported on this.