[xzilireight]

I grew up near Hiratsuka.
The best time to go is for the Tanabata festival. The city is very famous for it. Tanabata is always celebrated on July 7, so if your looking for something to do there now, I can't be of much help.
I would suggest hopping on the Tokaido line towards Tokyo. Go see Kamakura or Kitakamakura instead.
Kamakura was the capital of Japan in 1192, and it has millions of temples and shrines to visit.
You can also find good food; there is a yummy crepe place in Komach Doori, a walking shopping street next to the train station. You are also close to one of the big Buddhas (odaibutsu) and Enoshima island of the beach. You have to take the old enoden line from Kamakura or Fujisawa to get to Enoshima, but it is a great place to explore.
Kamakura is known for being a very posh area, and hiratsuka/fujisawa are known to be a little more "tacky." I always thought the area around Fujisawa station was fun to explore though.
Good luck!