In short, I don't see anything specifically prohibiting watering of gardens, but I'd not make a big show of doing it with inefficient sprinklers or taking a prolonged time about it. Your garden plants will likely do best with a low profile watering technique anyhow, and often will do best with an evening/early morning dose anyway so they have time to soak it up. Definitely consider mulching to help prevent excessive evaporation.
I was wondering that, too. Perhaps they're making a distinction between watering landscaping and watering gardens grown for food? I can't imagine they'd enforce the Monday/Thursday rule on you if you're just trying to keep your tomatoes alive.