It depends a lot on what is appropriate for the quilt, but I found that the quickest quilting I have tried that turned out well was using a walking foot and just doing a slightly wavy, irregular grid all over at about 2 1/2-3" intervals. I did one almost the size of yours in about an hour and a half. It actually took longer to do the binding. If it makes you nervous to take off without a guide, you could pin a strip of paper down and follow it within a short distance. You might need that only for the first line in each direction. Many blocks have seams that serve as handy mileposts. The grid can also be done on the diagonal.
For some designs, wavy streamers look nice - the same idea, only going one direction. For that, I would make the lines a little closer together, with some of them crossing each other here and there. I have used that on some placemats that were stitch and flip, so no quilting was really needed, but I liked the effect, and it was very speedy. Fairly big, random loops or hearts or leaves are all pretty quick to do, but I wasn't keeping track of the time, so can't give a good guess. If you're in a hurry, remember to select batting that doesn't require close quilting. If you feel your shoulders bunching up, it's time to give yourself a break and a stretch. Hope you enjoy your project!