You should do what works for you. Our first adoption, I didn't pump before at all because it was a stork drop. So I started pumping the day she was placed with us. I was able to get up to ebf by the time she was 2 weeks old, but I don't think that is typical.
Our second adoption we were matched ahead. I started pumping 10 days ahead because I couldn't commit to pumping before that and we weren't sure it would work out.
I am assuming you are using a surrogate? In your case I would have started pumping ahead of time (6-8 weeks) to try to build a supply for when the baby is born because you KNOW you are getting the baby (unlike adoption).
Even if you can only pump once or twice at work and then every 2 hours in the evening, once overnight and once in the morning, that would be better than nothing.
But again, only you know your situation.
Good luck,
Jennifer