Used to see many ebike washers around the city for 10rmb or less. Haven't seen one in ages. Don't worry too much about pressure because they just wash the wheels and plastic shell in my experience and do a great job.
I wouldn't bring a bicycle for the reasons mentioned by tiger above
Very Good Mechanic on the corner of Hongshandong lu and sujiatang lu. He often fixes our students bikes for free or just charges for parts. Only problem is sometimes I think he doesn't like customers to spend money so if its working he will just say its fine its fine
I have friends from Shanghai that cannot understand their grandparents because Shanghai Dialect is so heavy so maybe no Shanghai.
While there are issues with dialect and accents in Kunming there are also people here from any part of China. You can also make sure your school / teacher has standard Mandarin.
One great benefit of Yunnan is the great weather and access to nature. If you have one month in great weather intensively studying with a great teacher I think it is important to make sure you are in a comfortable place
April might still be cold some places in the North but Kunming has great weather at that time.