Here, in my race-director opinion, are the top reasons
1.) The traffic is fairly light (particularly at 8 a.m.)
2.) The park is easy for the ERC to work with (the ERC and the park officials have a fantastic and very respectful working relationship -- it's practically an ERC law -- thou shalt respect the park, the rules and the facilities -- that runners and race directors take very seriously).
3.) Virtually no intersections means you need very few road marshalls
4.) It's flat
5.) Abundant restrooms
6.) No dealing with city officials (I could say more, but...I'll leave it right there).

Here are a few local racing tips, hints that I've picked up over the 11 years I've been running around PISP. I'll post more later, for today...we'll focus on parking and potties.

1.) Stop at the ranger station to use the restroom before a race. There is always, always, always a long line at the race potties. Make a quick pit stop before you get there.
2.) If the race is at the Rotary...leave early -- it takes longer (one lane, slow traffic) than you think to drive out there and parking can be pretty limited.
3.) Consider parking at the ranger station if the race is at the Rotary Pavilion.
4.) Or, park at the P.I. Cookhouse pavilion and take the sidewalk over to the Rotary pavilion -- if you run, you can consider it a warm up. Bring a bag with your name on it...to leave your stuff in while you race (so you don't have to run back to the car).
5.) Do not ever park on the side of the road anywhere on the park -- rangers get very angry and you WILL get a ticket.
6.) If race is at Beach #1 -- never turn into the first two lots (unless you're very early). Drive down to, at least, the third entrance to Beach #1 parking.

Veteran racers -- got items to add to the list? post your comments below!