Unless ICP is having a new show opening the week of your arrival, it is unlikely to have a line - every time I've visited I was able to walk in and buy my ticket and enter the exhibit space without any wait. With MoMA, I think you'll be able to skip the ticket line and pick up your ticket at will-call, but there may still be a wait to enter. It really depends on what's up on the wall at the time. You may be better off going to the Metropolitan Museum (from a time-management perspective, and a budget perspective - the Metropolitan is (slightly) cheaper than MoMA). They have a photography show up right now that I want to get to see, having just visited its companion here in DC - the show at the Metropolitan is about photo manipulation in the digital age, as a counterpoint to the show that has now moved to DC about photo manipulation in the days before Photoshop (they have an excellent exhibition catalog which is well worth the price for the pre-Photoshop exhibit). There is not normally a line to enter the Metropolitan unless they have a blockbuster show, even though they are usually very busy, unlike MoMA.