I've had no problems getting on bustitutions with an unreserved thru-ticket stub. In fact, since you have to call to get AGR tickets that include a bus portion, I just order tickets for another day before so I can pick them up. You shouldn't have a problem.
The Del Mar trains they run (opening of the Del Mar races, etc) often are double consists of Pacific Surfliners; literally two trains stuck together, putting a cafe car on each end.
I think they've turned off the Wifi. I overheard a conductor say that it had something to do with interference going through camp Pendleton or something.