I have no idea where you are or what your business is, but judging by your post you were looking at buying a property in the campo?

If you could rethink your geography a bit and live in a city the internet connections are very reliable and you have a good choice of providers. No need to scupper your business plans if you are able to be a bit flexi.

or, if you are forturnate, like me, in the campo, you may be able to use a company such as iberbanda who provide wi-max broadband.

sg.

It's to do with astronomy - so sadly, ino. It's got to be as far away from towns / cities as is practical. Obviously there is a balance between being completely cut-off out in the boonies and being too close to "civilisation" for the light pollution to make the whole thing pointless. The problem is that in Spain, it seems that phone lines are very much an afterthought when it comes to providing services (to be fair, it's expensive to wire up vast tracts of the countryside, when you only have 1 customer out there) - way down the list of priorities after roads, electricity and water.
Talking to friends and neighbours in the area though, it seems that lack of internet access is a bit of a biggie. The net is probably more important to people these days than the ability to get british satellite TV.

How many people spread over what sort of area?

go to www.iberbanda.es - they have a coverage map and will send out an engineer to test if you are able to receive their service.
you will most likely need line of site to one of their masts.

steve g.