This must be the Year of the Bolt in the world of chard -- I'm having the same experience.
About your question that had three options -- personally, I'd do all three and see what happens. (assuming you have several plants to do different things with.)

Fwiw, the white-stalked varieties (Fordhook White/etc.) are slower to bolt...plus they tend to tolerate warmer weather without going bitter.

When they experience water stress, especially during summer, they'll start bolting, too.

This post was edited by nc-crn on Tue, Jun 18, 13 at 23:49

Pull them up and plant some more.JMO

Why not let them bolt? I let celery bolt once, and now I will never plant it again (this year I must have 2000 celery plants). Bolted arugula gives me two crops a year, with only one seeding. I don't plant cilantro, daikon, red mustard anymore.

I always let my chard bolt. I haven't had to sow fresh seed for years. And I continue to harvest the leaves on the flowers stalks. The small leaves and some of the flower heads go into salads. Bolting chard amongst Papaver somniferum on my allotment:

This post was edited by flora_uk on Wed, Jun 19, 13 at 16:38

If your chard is not behaving my first thought was towards weather and heat and/or water stress on the plants.

What about fertilizer? Is the chard getting a high dose of potassium somehow that is encouraging flowering?