I've never taken it myself, and my research has never conclusive answered this question: Can one actually take the Metrolink to Oceanside, then transfer onto the Coaster (paying all fares, of course).

I remember that the last time I check, the times were completely off... but I don't even know if they stop at the same terminus.

(And of course as I'm writing this, the Surfliner just rumbled past )