We looked at using Europa internet, but they said to get a good signal the modem had to be in the line of sight with their transmittor which is on the top of estepona mountain. We are in phase one of DV so cannot see the transmittor as it is blocked by Coto Real.
We tried a dongle from Vodafone. The first was 30 euros and didn't connect for more than a couple of minutes at a time, they refused to refund so I bought a different one and it worked ok, but was pretty slow. We also seemed to go through the 1gb cards in about a day and at 12 euros each was getting very expensive.
We only used the dongles for a few weeks whilst we were waiting for the movistar fixed internet to be installed. Now we have this on their 30mb service and it's not cheap but it is pretty fast and reasonably reliable by Spain standards.