Hi cindy:

Yo pude andar cuando la luz cambió. (''? don't get this one)
Tú no pudiste mover el coche ayer porque el camino de entrada ESTABA bloqueado.
Usted no puDo llevantarSE DE LA cama ayer porque tuve dolor DE espalda.
A la cena ayer, nosotros pudimos comer cuando a él llegó. '''''''?
Ellos pudieron salir a las tres ayer. (CORRECT)

Yo pude andar cuando la luz cambió.

I would venture a guess that this is something like,
"Pude cruzar la calle cuando se cambió el semáforo."

Mark, you are a genius. Of course!

Cindy, sorry, your sentence , like this, would not have been understood .

A la cena ayer, nosotros pudimos comer cuando a él llegó. '''''''?

ayer, pudimos comer la cena cuando el llego (no accents available)

we were able to eat yesterdays dinner when he arrived.

Oh, I see:

Pudimos cenar cuando él llegó.

remember:
comer.lunch
cenar: dinner

Usted no pudo Levantarse de la cama ayer porque tuvO dolor de espalda.

Eddy,I think your sentence should read like this:

We were able to eat dinner yesterday when he arrived.

And not:

We were able to eat yesterdays dinner when he arrived.

Unless of course,they were eating a dinner that was already a day old!

Heidita, do you mean that comer/lunch is for the noon meal, and cenar/dinner is for the evening meal? I'm asking because in parts of the U.S. where agriculture is still dominant, dinner is the NOON meal and supper is the evening meal.