I use a pre-paid wi-fi "dongle" in conjunction with my netbook while away from home so as to have access to the internet. Yes, I know that technology has moved on, but this system is tried and true and I find a netbook convenient.
Catch - during the summer at busy beach resorts there's a lot a demand placed on the networks. In our household we had users of all three networks, and all basically encountered the same problem: the reception bars can indicate good reception (often "excellent", but it does depend on where you are), but this is no guarantee that you'll have good access to the internet. It seems to me that the networks become congested so that, even though the reception is OK, response times on the internet are s-o-o-o slow that access becomes impossible (websites time out before a proper connection is made).
I understand that this is a seasonal issue, and at other times of the year, things are better. Moreover, I had no such problem last year.
It does depend on the time of day, so a "work-around" is to log-on at less popular times. In practice, this means early in the morning (seemingly Facebook users aren't early starters) or very late at night.