I compulsively check the reports for all of New England daily and on all the sites like this one as well as local anecdotal reports can be even more valuable if the character of the witness is high. Where are you coming from? Is travel with board a pain rather than a simple choice? There are good shops that rent good boards for reasonable prices.
Are you going with family or wife/girlfriend? I ask because you may want to sneak out to Nantucket as it can crank there when there's nothing much going on in the contiguous MA area. It's a heck of a place nonetheless. I'd get there regardless for part of the time.
Yes. If there is swell, you will have waves. There is ~40 miles to explore, much of it national seashore. I've surfed 3or 4 times at week for the last few months. We've had a good run. End of April - MidMay was excellent. It's hard to say what it will be in 3 weeks, but you wont know unless you go.
I don't have any experience with buzzards bay .. maybe your thinking horseneck? I would think Cuttyhunk and other islands would block ocean swell for buzzards bay, however I suppose there are conditions where surfable waves are available. I have heard anecdotal evidence that the cape cod bay side is surfable under the right (but rare) conditions.