There's one challenge however: the courts are hard courts, and they are really hard. Basically nicely painted concrete. That's not only tough on the body, but it also seems that the balls slide more than they bounce. Hitting the ball feels somewhat like hitting a stone with a wooden plank! Our rallies usually max out at 4-5 shots, and we tend to get pretty sore from playing. As a result, I soon decided that those courts won't ever be fun to play on.
Over time though, we figured out how to improve our experience by adjusting the other variables of the game:
Balls - This made the biggest difference. Playing in Germany for more than 20 years, I had been in love with Dunlop Tournament balls. They had simply been the best playing balls for decades. I disliked most other balls because in comparison, they felt too light, small, and felt-less. So coming to New York, I stuck to Dunlops for the first year or so. On this particular surface though, it made sense to try softer and lighter balls. We finally settled for Pro Penn ATP balls, and even liked them better if they had already been played once before, which made them more fluffy. That gave us a better bounce, more pleasant feel on contact, and longer rallies.
Strings - If your racquet suddenly feels a lot stiffer playing on a different court, it might make sense to try lowering the string tension. A couple of pounds can already make a big difference. If you happen to play on these kinds of courts often, you might even go for a softer string, such as a natural gut, or some of the softer multi-filaments or feel-oriented polys. Maybe try a (different) dampener too...
Grips - When you deal with an unpredictable or low and fast bounce, try using a new overgrip every time you play. That dollar is definitely a good investment if you feel and play a lot better. A new overgrip can soften the impact, and literally gives you a better grip while swinging loosely.
Effort - Speaking of swinging loosely, it's easy to tighten up when you play on a surface that you don't like, or when you feel that you need to work extra hard to transfer energy to the ball. As you might know, trying extra hard usually has the opposite effect - you put in more effort for less outcome. So stay loose - use your other hand to support the racquet between shots, hold your racquet in a way that someone could take it out of your hand when you swing it - and then adjust your tightness level a bit from there if necessary.
Forehand and backhand grips - If the ball comes to you fast and low, you might want to consider opening your grips a little. Or even a lot, and see what happens. When I step on those slippery hard courts for example, I always remind myself of the more open grips I used when I was teaching, and start out that way. This makes me a lot more relaxed and consistent out there. No use in overpowering or adding tons of spin anyway! Same might go for volleys, by the way - if the ball stays low most of the time, most of the volleys you hit will be low too. Experimenting with different grips can also help to make you a more versatile player, who can adjust to different conditions when it counts (or when you would like to have some more fun!)
Attitude - Last but not least, I don't expect to play good tennis on these courts anymore. I see them as a convenient option that allows me to see friends, have a workout, and get some hitting in. All things to be grateful for. With such a positive mindset and such low expectations, it will be hard be disappointed :)
So all in all, having a good time on those slippery concrete courts took some adjustments on multiple levels. And while I still don't love playing on those courts, we all now have a much better time.