Kate, you might be on the right track with some kind of wild lettuce. It does look like prickly lettuce which grows all over the US.
Here's a link to the database pictures:
Prickly Lettuce (Lactuca serriola)
Or it could be False dandelion, Hypochaeris radicata as already mentioned above.
It's not dandelion ( Taraxacum ) which has a very distinct leaf, like this:
Which is not a weed in my book. Actually dandelions are one of the best foods on the planet, very nutritious and good for spring cleaning of the entire body. Every part of dandelion is edible and good for you. (Of course, if it has been sprayed with pesticides, it's no longer good as food so don't eat if you have used chemicals in your lawn or don't know how the lawn has been treated).
