I'm new, with little to compare Purgertory Park to. It varies from wide & easy, to intermediate, to ' thank God I had a helmut on'. It connects to Prospect Park a well. Check out local web pages for more details & donate...they are doing great work in San Marcos.
From IH35 go west on Wonderworld Dr (RR12).Turn left at Hunter Rd & immediately right for the main trailhead (or the end of Dantes trail ((D-yellow makers)). The trail head for Dante- continue west on RR12, left at Craddock, then right at T. Follow to the end of the road.
http://www.singletracks.com/item.php?c=1&i=5028