Once when I was pregnant my dh actually asked out loud if anyone would give up their seat for me... after a few moments of silence nobody did. So dh had us get off and wait for the next bus.
IMHO I think it is sort of rude to get on a bus
expecting someone will give up their seat for you. I
DO think out of kindness someone should have offered, but for your DH ask out loud to have someone give up their seat would have made me not want to do it (especially since there was obviously another bus coming).
I think if you are someone (pregnant, injured, handicapped, with small children, etc) who knows that you will not be able to stand for a bus ride, you need to get their early to be sure you will get a seat, or wait for the next bus and not get on a full bus
expecting that someone will give up their seat for you. Just consider it a bonus if someone does offer.
That being said, I would hope that people would be kind enough to offer. I am a 35 year old woman, and I do give up my seat if someone needs it more, but if I have waited in line for the same bus and you happen to get on later after it is filled, I probably won't offer my seat unless you are elderly, obviously handicapped, or very pregnant. Otherwise I will figure that you have the option of waiting for the next bus, and if you decide you don't want to wait in order to get a seat on the next bus, then you choose to stand.
I probably don't feel that way in all cases, but I was in a situation one time (not at WDW) where I got to the bus stop early because my legs were so tired and I wanted to make sure I got a seat. The bus waited for about 10 minutes as it filled up (the next bus would be there in 15 - 20 minutes). As we were starting to pull out, a family with Dad, Pregnant Mom, and 3 small kids come running up. The bus stopped to let them on, but then once they were on, the DH in the family started arguing with people who would not stand up to let his wife and kids sit down. It turned pretty heated. This is the type of situation that really makes me angry when people think it is their
right to sit down, even if they get on an already filled bus.
Go ahead and flame me, but remember - I DON'T THINK EVERY SITUATION IS LIKE THIS. I KNOW NOT EVERYONE DOES THIS. MY OPINION ONLY REFLECTS THIS ONE KIND OF SITUATION.