DD and I are doing this race, as well as the Princess. Since I pay for the rooms and races AND MY CENTRAL AIR CONDITIONING WENT OUT TODAY!!
If we stay at one of the motels directly across from the entrance on Harbor Blvd., how long a walk will we have to get to the starting point of the race? Is the entrance on Harbor Blvd. the only pedestrian entrance into the park? I was looking at motels on Katella which look close to the beginning and end of the race but are far away from the entrance to the park. We want to go to the parks for a few days.
Sorry about the Air Conditioning!
As for where you stay, that's a really tough one and it'll pretty much come down to which spot you want to be closer to.
If you stay on Katella, you can do 1 of 2 things. You can walk all the way around to the Harbor entrance which would be a trek. Also, If you walk down Disneyland Dr, right past the Paradise Pier, there will be a parking lot. (The one closer to the DL Hotel, not where we finish). If you cut diagonally through the parking lot, you come out at the end of DTD by the AMC Movie Theater. From there, you can either catch the Monorail(just past Rainforest Cafe) which will take to into DL at Tomorrowland or walk through DTD to get to the Main Entrance for both parks. It may sound confusing, but once you get there it will make sense.
If you stay on Harbor and closer to the parks, you would just do the opposite. Either walk down Harbor to Katella then DL Dr for the race or cut through DTD and the parking lot down DL Dr to the staging area/start line.
To give you an idea of distances, DTD from Harbor to the DL Hotel is b/w 1/3 and 1/2 mile, from the corner of Harbor and Katella to the starting area is about 2/3 of a mile. It was easier before they started building Carsland if you were staying on Katella, b/c there was a shuttle you could catch by going in the parking lot across from the Convention Center, but now Cars is there so no more for that.
It may sound a little overwhelming never being there before, but the parks are together and the hotels pretty much all surround the parks. Once you get there it won't be that hard to figure stuff out. Plus race morning if you do stay on Harbor, you'll see tons of people treking out to the start so you can just follow them!
Another thing to think about is that if you're going to the parks for a few days, it would probably be easier to stay on Harbor then walk from Katella every day and night, b/c the race is only 1 morning. Yeah, you might be sore afterwards but if you go to the park after the race and Monday, your legs will thank you for the little less mileage.

Plus, they might have shuttle race weekend. If you look at the DL 1/2 website, they have a transportation link has a map that'll list hotels that the shuttle will stop at Friday through Sunday. The shuttles will take you to the Harbor Entrance. They don't have anything up for the Tinkerbell yet, but, at least for the race weekend, you won't have to walk far if they stay the same and you stay on Katella.