Glad to see you are making the trip. Off of Rt. 26 you turn onto 7 Points Rd. and travel about 2 miles when you see "Jim’s Anchorage" on your right look for a sign at the crest of the next hill and you make a left onto Baker’s Hollow Rd and travel about another 2 miles to a parking lot on your right that puts you in the middle of the trail system. Enjoy! There is a map in the parking lot and maps and signs posted periodically along the trail. The color coding of the trail map is like ski trails except instead of difficuly the colors just mean distance from the parking lot. There is only one true rock garden and if you want to experience that take th entail to the right out of the parking lot.
If the weather has been extremely wet before you arrive you may want to save your trip for a dry weekend. The shale sections of the trail system can become sticky and even downhill section take a lot of energy to pedal. The entire point of Alligrippis is to go fast and enjoy the twisty, turning rollers at some sort of speed.
There is a fantastic bike shop in Huntingdon, PA http://www.rothrockoutfitters.com/ that can answer condition / trail questions for you.
Boxer’s in Huntingdon is a great post ride establishment and also the Spruce Creek Tavern in Spruce Creek is also worth a stop on your way home for food and drinks.
Also, if you like to trout fish, the Little Juniata is not far away (Spruce Creek) and is a Blue Ribbon trout stream.
Hope you enjoy your trip.