If you are catching the train from 4th and King I would not anticipate any problems, particularly at that hour. I would suggest showing up about 15 minutes early for the first couple of commutes so you are assured a spot and get a feel for how crowded your train is with bike commuters. Some trains are more crowded than others. However, rarely do bikes get bumped at the 4th and King, which is the beginning of the line for south-bound Caltrains. Same advice goes for the reverse commute from Diridon to 4th and King. But again, Diridon is near the beginning of the line for north-bound trains. So, the train probably won't be at its bike capacity yet.