Sean,
ibiza, as i'm sure you know, has a huge range of dance music events and has done it all from hip hop to drum 'n' bass to jungle to trance to hard house, whatever. so don't let promoting a type of genre of dance music put you off.........
san antonio is your best bet for a starting place for venues. in the past events like sundissential, HQ, Nucleuz, tidy, lashed have all had reasonable success (at eden mainly) running stand alone nights but they have also done this with some serious finance to promote them.
what sort of size venue are you looking for?? presuming that it's small to medium size venues, then your options are 2 fold.
1) back room of a club promoted by another night.......i.e. an alternative to the main event , which will broadly appeal to the punters attending the main night. E.g. Judgement Sundays, Gatecrasher Classic, euphoria/tidy @ es paradis. The problem you will have here is many of these nights have established support/2nd room events and breaking them will be difficult. The only way to do so is by marketing the old fashioned way or better still going to ibiza and flogging them the idea. (look at the confirmed club listings section of the forum for potential contacts) if the main promoter likes your ideas then they could give you a shot in the back room, even if just for one night or a few hours. do your best to figure out which nights have strong back rooms and which nights are actually looking for a decent guest support.
2) Go for your own event in a smaller venue, like a preparty bar or smaller club in the west end. The trouble here is that, historically, many of the venues such as nightlife and play 2 have their own DJs who play a wide range of more commercially tinged dance music every night, they often don't host guest nights every night of the week. The other problem is that trying to obtain one of these venues is almost impossible unless you are over in ibiza doing it face-to-face. Think of it this way, in the UK most clubs open 3-5 nights a week and always looking for events in order to fill the clubs, so when you come along with your night, if they like it - you're in. In ibiza everything is open 24/7 and therefore a bar is more likely to employ a resident DJ (even all the bars in the west end do) to play the music most likely to appeal to as many customers as possible. These venues will be free to get into as well, so if you did get a gig you'd have to do everything for free and cover any promotion of the night you wanted to do.
I think the main problem for you sean is that the type of venue you're event would be most suited too (e.g. a small-medium sized club) doesn't really exist in ibiza other than a few in the west end and the issue here is that no entrance fee is paid so guest events/nights are not promoted in the same way as they would be if an entrance fee was being charged. In context, the place will be being plugged for the drinks deals and fit girls, rather than for your music.
Last but not least, 100% of bar owners in the west end or in the bay of san an would allow you to host a night at their place if they thought you could pull in the numbers (thus, increase bar takings). The only realistic way for you to do this is to be pounding the streets and selling your night to them.............it's quite likely someone will give you a chance in their bar one night (or part of one night, if the music is putting off the punters).............if you get the chance, work your bollox off promoting the niche and getting all your friends in there, and make sure the word spreads around the workers too as often they dictate to the masses what/where is hot and what/where is not.
good luck!
. 
