International Gospel Uptown closes 6th av from 42-56 sts 10am-3pm Saturday. Street fair also closes 8th av from 14-23 sts 10am-7pm Saturday.
that's avoiding 6th avenue i'm guessing it'll get shut down at 40th street or 38th, only one option really seems appropriate stay east when heading uptown for rides. if you pick up under 23rd at 6th avenue make your turns before 23rd, like 20th street perhaps, the earlier the better, just avoid it all together, try to be uptown and do crosstown trips, and when you get a ride going downtown make the crosstown trips well above 56th street (like 79th) or well below (like houston) i'd go back uptown empty on the fdr drive or 12th avenue and work for a straight trip downtown again with a fare.
if you feel bold there will be heavy demand for rides from penn station to the javits center, but really that won't be too profitable, at around 10am up to 1pm i guess. when 6th avenue opens up again, or depending on how much this closure blocks up crosstown traffic, there will again be a lot of demand for passengers at javits center again.
VVanderbilt Ave. bet 42-46 sts closed 10am-7pm Saturday for Day 2 of Earth Day Fair. so i;d forget about going to grand central station to get fares, because turning is illegal on madison avenue, and 6th avenue is closed at 42nd, wow, your not going to even get to grand central, and you're not going to get out either.
so the plan: upper west, upper east, do crosstown trips there. take anything on the downtown avenues for a relatively smooth ride, but that crosstown traffic will be a nightmare in chelsea and midtown. once downtown, head uptown on the highways to get fares uptown going downtown again, or perhaps try your luck with lower east side, eeast village getting something uptown staying on the east side, but chances could be they could go to midtown and with 6th avenue closed it'd be tough.