>So do women with two uteruses have two menstrual cycles?

No, they don't. Uterus didelphys is caused by two tubes that normally join during fetal developed not joining. There are still only 2 ovaries. Though the bleeding might be irregular due to physical reasons.

Even if ovaries were doubled, there wouldn't be two cycles as hormones are centrally regulated and wouldn't be able to target specific ovaries.