From an instrumentalists standpoint, I would classify it as a "decent" program within a liberal arts environment. For an average student playing at a mid-range level, it would be a nice program to continue playing while in college. It is not necessarily a program I would steer a serious instrumentalist looking to develop a high level of proficiency, or a potential professional performer.
That being said, I have heard very good things about the organ program.
The faculty listing shows two voice instructors, and the department website indicates the vocal ensembles do some touring.
Given the total enrollment of a bit less than 3000, I'd guess the music students number around 100-150. I could find no info indicate actual size of the program.
Holy Cross is also a member of the Colleges of Worcester consortium, allowing cross registration at member schools. http://www.cowc.org/
Off the top of my head, non of the member schools are known for their music programs. Holy Cross appears to have the strongest across the consortium members (I know for example that Becker College has NO music program), but it may be possible to investigate ensemble opportunities at WPI among others.