Two years ago, EB, Chi-Sea, upgraded from roomette to bedroom at lowest bucket price for bedroom. (Bedroom was at highest bucket price) Asked nicely when the Conductor took my ticket in the Metropolitan Lounge about the upgrade. Upon departing Chicago, checked with sleeping car attendant as to exactly what bedroom(s) were open for my entire journey and informed her as to my desire to upgrade. Conductor did not forget me, and stopped by to check to be sure I was the passenger wanting the upgrade. She was back with me within 10 minutes with price. I took the bedroom and gave the Conductor my cc to charge the price difference. My cc was never charged by Amtrak for the upgrade. I either got lucky, or someone felt sorry for me.
Last year, TE, Chi-LAUS, upgraded from roomette to bedroom at lowest bucket price. (Bedroom was at next to highest bucket price). I checked with Customer Service Counter in Chicago Uniion Station regarding the upgrade about 30 minutes prior to boarding TE. CSR gave me the price which was the lowest bucket price (she actually told me this, but I already knew). I took the bedroom, and she made the necessary change in the reservation. Was then sent over to the ticket counter to actually exchange the ticket for the new ticket showing the bedroom and to pay the price difference, which was something like $160.00.
Three weeks ago, Silver Star, Orl-Was, wanted to upgrade from roomette to bedroom. (Bedroom was at highest bucket price). Checked with sleeping car attendant for availability of bedroom, since there are only two plus handicapped on a viewliner sleeping car One was available entire journey. Attendant informed Conductor who stopped by after leaving Winter Park, as I was told he would do. Conductor was back in about 5 to 10 minutes with price, which was the highest bucket price. I thanked him for checking and declined bedroom. Bedroom did stay empty all the way to Washington DC.
Always ask Conductor politely, which I know you would. Also, you might inform the sleeping car attendant that you are interested in the upgrade, he can check his passenger manifest to see if one is available for the entire journey, or just a portion of it. I also call Amtrak about an hour before train departure to check on the availablity of a bedroom and the price I would be charged for it if I changed the reservation over the phone at that time. You can always go on line and check too. This way I can check to see if it is even worth asking for an upgrade, and the price I am given on board compared to the price I am given an hour prior to departure -- if I am being given the lowest bucket price for the upgrade or the highest bucket price. I usually know beforehand what the bedroom bucket prices are.
So you can read, it has worked different ways for me. I will say, however, all Conductors have been very nice and prompt with checking the price for me.
Good luck, and hope you get the upgrade for the price you want.