One other way to get to Seca from the south is between Highway 101 and PCH 1. You can head to the San Antonio Lake area via route G14, connect with the 101 for about 1 mile, then bear left to route G16 which turns into Carmel Valley Rd. Carmel Valley road drops you out right in front of the Laguna Seca Entrance off the 68. What I understand from my bro, its a twisty road and no better way to ride into Seca. Don't get me wrong, PCH 1 is great, but Carmel Valley Rd sounds like a hoot!
FYI: Me, my bro, and some friends will be riding from San Diego North County to Seca. We plan on leaving around 10:30ish this Thursday morning. If you are interested, post a reply!