For a short move with a smaller tank, you can consider leaving the sandbed in the tank.
Wet sand is seriously, seriously, heavy and it is tough to move a tank without getting it out. I just moved my 65g that had only about 2 inches of wet sand in it, and I think it was heavier than my empty glass 120 was to move. Really heavy, my end was about THE most I could possibly carry, and I thought I would not make it to the car.
When you move a tank with a sandbed in it, you do have to keep it pretty level, because all that extra weight does add stress to the seams. If you have a small tank (20-30 gallons or so) I have found putting a board under the tank and holding that makes moving it easier.
When you fill the tank back up, be sure to put a big bowl in the tank that you pour the water into to reduce sand disturbance.
Now if you can't carry the tank safely and level with the bed in it, I think trashing it and putting in a new one is the best bet. Old sand beds are smelly, heavy, and really really gross. Much easier to put in new sand at the new house, save a scoop of sand from a particularly live area before you take the tank down to get the critters going again.
I am also one who feels that these beds get chock full of gunk and need to be changed out every once in a while anyway, what better time than during a move?
