To answer your specific question, yes, one can upgrade on board from a roomette to a bedroom. If one does that, one then gets the lowest bucket price for the bedroom. In some cases, if you hit a high enough bucket for the roomette, you could find that you've already paid more than the lowest bucket price of the bedrooms on that train. In that case, you would be able to upgrade to the larger room for free. And all simply because you asked on the right train at the right time.

Now all that said, in your case for the trip that you've described below, I rather doubt that you'll find a conductor willing to do the paper work for such a short ride that doesn't even involve an overnight. Most likely you'll just get a "we're sold out response" from the conductor, because it is simply too much work for such a short ride. The conductor might be a bit more willing to upgrade from coach to a roomette for that ride, but even then I wouldn't bet on it. It will come down to how customer service orientated is that particular conductor.

If you already have a roomette, then you'd probably be better off trying to sweet talk your attendant with a nice tip to let you sit in a bedroom, assuming that one is available.

You can get some idea, but not the full picture, of what's available by pretending to book your trip and setting the number of passengers to 8. When you then go to select the type of accomodation you desire, the system will show you a maximum of 8 roomettes and 8 bedrooms. If the dropdown shows less than 8, then you know exactly how many rooms are currently left. If it shows 8, then you have no way of knowing if it is really 8 or if it is more than 8.

One note, I recommend actually selecting the quantity of 8 and asking it to price the upgrade. I have seen cases where the system shows 5 bedrooms for example, but if one tries to price that you'll get an error. In that case keep decreasing the quantity until it does give you a price. Then you'll know the exact quantity for that accomodation left.

If you want to be more accurate than that, then you'll have to either call Amtrak or visit a station with an agent, and hope that they are nice enough to actually look up the info for you.

He shouldn't do that, but who knows. However, if you meet a really nice conductor he/she might be willing to give you a quick tour of the car.

I have seen a story where one Parlour car attendant used to do that, but AFAIK even he wasn't really supposed to be doing that. However, that is all academic now, since Amtrak eliminated the attendant's position for the Parlour car. It now runs unstaffed.

One other word of caution here, if you are planning to get a sleeper or any size, simply for the purpose of seeing the inside of a Parlour car, then you should know that not every train actually runs with one. And there is no way for you to know that, until the train actually leaves LA that morning.

At present there are only 4 Parlour cars listed on Amtrak's active roster. At this time last year Amtrak went from using 4 distinct trainsets to cover the CS route, to 5 trainsets thanks to UP's lateness. I've not heard if they've gone back to 4 trainsets since things have improved some since last year.

But if they are still running with 5 trainsets, then already you can see that at least one set does not have a Parlour car on it. And of course those cars need routine maintenance and inspections, and they are also some of the oldest cars in Amtrak's fleet so they tend to break down a bit more than others.

Therefore at best, Amtrak probably only has 2 to 3 of them running at any given time. If there are 4 trainsets again, then the odds are a bit better that you'll see one on your date of travel, and worse if there are 5 trainsets, but I sure wouldn't want to bet on one being there for the date you decide upon. So if the sole purpose of getting the sleeper is to see that car, I don't think that I'd waste my money with those odds.

The eleven month rule should not be applied as a hard and fast rule. One must be careful to avoid picking a holiday period 11 months out, as Amtrak may not have assigned any rooms to the lowest bucket for the days leading up to and trailing the actual holiday. Additionally, if the 11th month is June, July, or August, I would again not recommend using those prices as a basis for determining the lowest bucket as Amtrak again doesn't always price any rooms at the lowest bucket price.

The best source for knowing the lowest bucket price can be found in the Amtrak timetable on page 116 of the newly released timetable. Of course if you aren't traveling between endpoint cities listed on that page, then you'll have to guess at what the lowest bucket might be from your departing/arriving points. But using that table in the timetable, in conjunction with the above suggestion of pricing months ahead, you should be able to get a good idea of what the lowest bucket should be.