Rostock itself is a nice little city, interesting and compact centre, nice seaside resort out at Warnemünde. Cost of living is actually not that low: 2nd most expensive in former East Germany and rental prices are above the German national average (not just the E. German avg.). Prices drop off pretty quickly though going further from the city/the coast - but if you wanted to live in or near Rostock you pay about a 50% premium compared to in a village nowhere in particular - around Laage itself is probably a bit cheaper but still not rock-bottom (those in München will probably dispute me saying that the prices here aren't cheap though!).
If you're in to forest, lakes, coast and solitude then MV is great. If you want socialising there's plenty of bars etc. in Rostock. If you're looking for other ex-pats then you're probably lookin in the wrong place. I've yet to meet any english-speaking expats here, although to be honest I've not tried to either (yes, I have
gone native). The Volkshochschulen offer courses in German as a foreign language, as does the
language centre of the university. No idea what they're like though since I spoke some before I moved here and have picked up the rest by just immersing myself. I've even just about got the hang of most of the grammar now...
I'd not try living near Laage and working in Berlin: the train Rostock-Berlin takes about 3 [s]years[/s] hours (although I saw somewhere that there's meant to be an IC(E) on that route starting next year, but given that most of the track is pretty knackered it won't be a 300km/h job for a while) and to drive it is also about 2 hours or more, depending on whereabouts you're trying to get to. It's actually quicker to get to Hamburg from Rostock (~2 hours on the IC, and there are quite a few people do that commute every day as well as plenty who stay over there during the week while the family is here, also about that to drive it, depending on how fast your car is since the A20 is largely unrestricted and empty) so if you are set on/forced into a long-distance commute you're probably better off looking west, but don't bet on not finding anything in Rostock itself - particularly if you're flexible and not too bothered about salary. It does probably help though to have reasonable German (conversational level) before you start looking.