Amsterdam indoor : skatepark Noord, very street-y-, skateshop either Ben-G or Toms (indoor micro ramp), i prefer the latter.
Utrecht: SPU (SkatePark Utrecht) big indoor, wood, some spots outdoors but not too familiar
Rotterdam: most (enough) spots all cruisable distance from eachother whereas Amsterdam a bike is mandatory really. Big concrete skatepark in centre of city called Westblaak, from there people usualy go around.
either way all cities within 1.5 hours by train from eachother
but yea, if the weathers good and your in Amsterdam youll find people at Olympia, lights there aswell untill 10 (gets dark at 6 now)