I think you need to be a bit more specific, like...
..what time of year?
...the town or the bay?
...self catering, half board, room only?
...apartment or hotel or hostel?
...your overall budget? (how much you want to spend)
...where you want to fly from in the Uk?
any other preferences like close to the beach, nightlife etc etc. I dont think cheap and best go really to well together

ok i admit very vague....

Right me and a friend, both ages 20.

I am only looking for going for one week between the dates 28th July - 5th August.

We are looking for something with a lot of nightlife, as we love to go clubbing...

So we arent sure where exactly all we know is san antonio...

Will only have aa budget of £1000 each roughly, .....

Cheap and best don't go well, but i mean the best we can for the budget that we have...

thanks in advance

right...lets see if i can help a little

Well for 2 young lads, san antonio is a great place and you would probably be best off in san antonio town which is where the 'west end' which i assume will be you type of thing (its a bit like a noisey city centre pub place, gets dead packed, loads of youung people etc).

The only problem with the time of year is that its the first week of the school hols so prices will be more expensive than usual. the cheapest way might be DIY, which means you book the flights separately and the accommoation yourself, here are a few cheap flight sights where you can put in you dates and destination and it will come up with the price
http://www.thomsonfly.com/en/index.html
http://www.easyjet.com/en/book/index.asp
http://www.flightline.co.uk/flights/cheap-flights.htm
http://www.jet2.com/

Once you have your flight have a look for accomodation, again here are some sites you can book through, quite easy to use, just put san antonio, ibiza in and it will come up with some choices from cheap hostel type in the centre of the town to more upmarket hotels depending on what your can afford
http://www.alpharooms.com/
http://www.bedbookers.com/
http://www.wintersunshineholidays.com
http://www.tripadviser.com
http://www.ibizaholidays.com/default.htm
http://www.holiday-rentals.com/Spain/Ibiza/Sant-Antonio/r2123.htm
http://www.ibiza-hotels.com/

Dont expect anything dead cheap especially for the flights as your
booking a little late.

Also check out http://www.spotlight-forums.com/ theres some really good info on ibiza, just search for san antonio and you should get some good advice

In san antonio there is only Eden and Es paradis for clubs which are okay depending on what music scene you are into, futher out towards ibiza town you will find other big clubs such as Space, amnesia etc. the west end is buzzing if you like that type of thing but theres also the sunset bars where some of the clubs preparties are held.

For your budget you should defo find something, best to find something as cheap as possible and keep your money for the beer and clubs as they can be very expensive, the clubs i mean

nice one, thats a great help will look at some now!!

Excellent help there Lukey

pleased I could be of assistance, at least its a start

also
http://www.findmeaccom.com

have some decent cheap rooms