Abbie my Goldendoodle

I have a 16 month old Goldendoodle, Abbie. We are first time owners of this breed. Previously, we had a Golden Retriever but decided against another one after she died since we didn't think we'd ever have another like her. So, we decided to get a mix and I know that poodles are fun and smart and thought the combination would be nice. Abbie is really smart and has learned quite a few tricks that she can do either on hand or voice commands. I use a harness for walks because she is so strong and gets excited if she sees another person walking their dog. I can USUALLY get her to sit and stay until they pass by but not always. A treat is also involved in obeying. We still have a significant problem, however, when people come over. She jumps up on them to the point of being truly annoying and we have to harness her again. Does anyone have any great tricks for changing that? The sit/stay does not work here. Thanks for any info.
Gretchen aka gtlane