Welcome to All Things Plants, @reginajsmi
Are you in Michigan? (I'm just guessing that from the "mi" on the end of your screen name... ) or, if not, where? (planting in Florida and planting in the northern states, as an example, are two very different things!)
I've gardened successfully in sandy soil, but you need to add plenty of fertilizer and lots and lots of water ! Pumpkins (and any kind of squash) need lots of water, and with sand it drains through pretty darn quickly.
Going on my first impression of "Michigan," you would want to plant the pumpkins after the last frost; I always start my seeds indoors in early to mid May, and transplant them to the garden around the beginning to middle of June. They do need a fairly long growing season.
Hope this is somewhat helpful and that we'll be "seeing" more of you around the site !