I disagree with the above posters. I'll give you my input as a grad student at a decent, fully-funded program and have been on our admissions committee (reading all files, etc) and have been involved in too many 'recruitment weekend' type events (i.e. one is too many). Keep in mind that this is only my experience with profs in my department; perhaps this is not the norm.
I didn't go to my own recruitment weekend since I was, like you, engaged at work. When you tell the profs that "I can't come, I am collecting data," they hear "I am serious about my work/research and will apply the same work ethic to grad school if accepted." That's definitely how profs in my department think, and is basically what they have actually said when discussing recruits who can't make the recruitment weekend trip.
Furthermore, since you were already invited out of a likely huge number of applicants, they already think you are good. Now, ask yourself this question; will most of these academically distinguished recruits be able to be even more impressive in person than in their totally inflated letters of rec, statements, and undergrad grades? No, they won't. Which illustrates the fact that these events often CAN hurt you but OFTEN cannot help. They probably set up a phone interview instead, where you'll just talk with your potential advisors for 30min or so.
Anyway, if you were applying to my program, I would advise you not to come. Hopefully that is the case with your program.