its the distances that will kill ya on a bicycle. I am talking from experience, I spent over 18 months travelling by bicycle all over aisa in '82. The heat will get to ya as well and on a bike ur not going to head back to ur air con room and have a siesta and return for the sunset. It gets really hot there
Angkor is best expericneced with a moto tuk tuk for about $15-20/day that will pick ya up at 5 am and then be there for u all day untill u say good night.
I still feel $5 a night is at the low end, sure u can find places but for me i prefer comforts. air con and hot water when its 34 out side makes a better vacation and it only costs ya $12-20/night
AS far as travelling around, there are busses all over to where ever u want to go although no trains. Also taxis which can be shared and boats between places like Battambang and Siem Rep and Phnom Penh and SR
I still hold spend more-enjoy it more and come back....
Tara; is this ur future husband that you met?