There really isnt a way to tell whats going to happen, or if he is ready. I mean look what happened, he went to one session and has already changed his mind about leaving on Friday. I wouldnt read too much into anything at this point.
My husband started with an outpatient program but he was working and it required him to go in the evenings and on the weekend. He didnt like it and he quit. He decided he wanted to go to an inpatient and picked one out of state, but he never got to that one because long story short, he went on a bender and ended up in a local inpatient that was based on AA. He didnt like it at all. Doesnt want to be in that program and so he left that one. But the key is that he still knew he had a problem and he kept looking for what would help him. Stuff doesnt always happen in a straight line is my point. He began therapy with a dr who specialized, and there have been ups and downs but its been progressively better since that point.
We can look for signs but still be fooled, because things change, outlooks change. Glad you posted, hope all goes well, and you can have a good time on your trip this weekend.