skaballet
Diversity workshops are great. However, a lot of people recommend visiting the schools on a different day if you are able in addition to the diversity days. Just understand that schools put a lot of effort into these weekends and it isn't exactly representative of a normal day. Regardless if you can visit schools before you apply I encourage you to do so.
I would definitely agree with skaballet. I attended a diversity weekend at NYU and they really went all out. The entire weekend they had about 50 minority students working with us as we attended seminars, dinners, clubs, etc. So while it was a great experience, it was definitely very scripted. It's not like they're going to be putting on conferences at the Metropolitan Club every week. So to get the real feel you really need to go another day and catch them with their pants down

.
But, as far as getting enough information to write you essays the diversity weekends should be enough. You get to meet a lot of people and visit the school and city. From that you should be able to tell if you would like to live in the city and if you mesh well with the type of students that go to that school. Then if you get accepted you can always go back on a regular day to confirm you thoughts.