Vodafone Spain offer various SIM only prepaid options.
If you want also to make International calls they offer an International SIM .
EU calls 1.2c per min and EU mobile calls 11c per minute. One days Web 150MB allowance EUR4
a day. That would do for non heavy usage ie: emails / iMessage ,basic browsing but not for TV
They also do a stand alone data packages.
If you just want mostly data look at ''Smart 16''
Prepayment Rate Smart 16:
Now with 1.5 GB
Now your rate Smart 16 has many more MB
Enjoy for only € 16 (€ 19.36 with VAT) for 30 days:
Unlimited calls and texts to all Vodafone yu:
100 minutes to talk to anyone, anytime, anywhere
Maybe best to visit a VF
store and ask them to set it up. You buy a top up card for EUR20 and then buy the plan by dialling * 505 * 23 #
Im sure there are many other companies offering rates but Im only aware of the VF
one in terms of products etc...