Almost every hostel will have wifi and you'll be able to find the occasional Starbucks or similar place with wifi so it just depends on how often you want to contact them. If say, once a day on average is enough, then I wouldn't worry about buying any plan. 

Mc Donalds restaurants in Europe generally have wi-fi.

You can also get some connectivity by buying a pre-paid phone SIM - you can get those at airports

and telecom outlets (most supermarkets will have them). I purchased SIMS for the same phone in the UK and also France -- depending on your usage, it might last 12 days. My French SIM lasted 8 days of usage -- having mobile internet was useful for finding accomodation and for things like maps.google.