"I wish you could come with us"

"I wish you could come with us"
 

In English, we would say "I wish you could come with us" in a situation where it is not possible or likely for the other person to come. The "wishful thinking" of a situation that can't happen is implied in the word "wish."

How can the same thing be said in Spanish? I might say "Me gustaria si pudieras ir con nosotros" but I don't know if this implies that the other person can't go.

Hmm... If you use "si", I might understand it as "do what you can to be with us".
I'd prefer :"me gustaría que pudieras ir con nosotros"/"ojalá que pudieras ir con nosotros". This expresses the wish, but you don't put pressure on the other person.