re: NYC trip in May. Recommendations?

Others here will be better with standard tourist recommendations. Since it's your first time in the city, I doubt you'll go, but let me know if you're planning on Brooklyn. Dad and sister live there, so I've gotten to know it well (Williamsburg, specifically).

I don't spend too much time in Manhattan, but I have a couple cousins in West Village, so that's where I hang mostly. In the neighborhood, Blind Tiger is a great craft beer bar, LB is my favorite cocktail bar, Joseph Leonard is my favorite restaurant, and John's is my favorite pizza (think many agree). Speaking of pizza, I maintain the most-underrated slice in Manhattan is NY Pizza Suprema. It's on the SW side of MSG / Penn Station, so it's easy to miss, but I try going for a slice whenever I fly into EWR.

Regarding the Subway conversation, I'd approach it like any other big city - just be aware of your surroundings. Personally, I've never felt unsafe on the MTA, but I tend to stick to the Subway during daylight and prime dinner hours.