I think you'll find Citi Field a good environment for a visiting fan. As with any city, there are idiots who will treat you as "the enemy", but for the most part, New Yorkers are a friendly sort who you can strike up a conversation with you as long as you're respectful. Worst I've had it was a run in with a drunk fan who didn't like where I was standing on Shea bridge. He got tossed and I got an apology from Citi security. I chalk that up more to the alcohol than him being a Mets fan, though.
I enjoy Citi as a place to watch a ballgame, not as cozy as CBP, but real good angles, and nary a bad seat in the house, much better than that monstrosity in the Bronx. Food is good for the most part, lots of choices, as well as standard stadium fare. Be prepared to watch 2-3 innings from the Shake Shack line if you choose that route. Can't go wrong with authentic Chinese on Main St in Flushing, though...good call.
Driving to the stadium on game day is tough, leave extra time obviously, but they do have plenty of parking. Think Schuylkill expressway-type traffic on game nights, and Pattison Av-type lines to park when you get closer to the stadium. If they're doing fireworks that night or have a post-game concert, it will be worse.
I'm a big public-transportation guy, so my preferred route is driving to Staten Island, taking the ferry to Lower Manhattan, taking the 4 5 train to Grand Central, then hopping on the 7. They're building a tourist trap on the Staten Island side of the ferry these days though, and sadly have eliminated a lot of ferry parking. Another option is to drive to Harrison, NJ and park in one of the many lots that surround the Red Bull stadium, hop on the PATH train to WTC and get the 4 5 to GC for the 7. Quick access to the NJ turnpike to and from there.
Hope this helps, enjoy your day!