Gao Yang and his companions left Los Angeles and were on their way to Portland. They were going to Morgan's home. Although Morgan had residences in many places, including Los Angeles, his real home was in Portland. So when Morgan planned to invite Gao Yang and company to his home, the only option was Portland.
The distance from Los Angeles to Portland is over fifteen hundred kilometers, which is quite far. However, Morgan had already flown somewhere with his private aircraft. He was very busy and couldn't possibly stay in Los Angeles. Moreover, he did not have time to send his private plane to pick up Gao Yang and company for Portland. And taking a commercial flight presented problems, firstly with Gao Yang's group's passports, and furthermore, they had all their gear from rescuing Bob with them, which included a heap of firearms and ammunition, naturally impossible to take on a plane.