We would like to travel to Lijiang in mid july. How is the weather and how do we get there?

It is the rainy season in July. The temperature may drop to 5-10C after the rain, so bring both rain gear and warm jackets with you. However, the radiation of the sunshine will be rather strong if in the sunny days then, so suntan lotion and sun glasses are also advisable.
You may fly to Beijing or Shanghai first, and then fly to Lijiang directlly, There is no direct train from Beijing or Shanghai ti Liajiang now.
For China visa, I advise you apply for it from the China Embassy in USA in advance, since it's hard to get an on-arrival one when you arrive in China.