Knott's is about a 15 min drive from Disneyland, as far as the best way, try here for more information http://www.airportbus.com , click on knott's from the homepage.
if you like lots of roller coasters--it is not disneyland and it tends to be a lot dirtier. also, there is not as tight of security compared to d-land but just my bias....................the chicken dinner is fabulous tho'