I decided to use Pretty URLs. That was OK.
But I could also set a "Canonical URL" on the same form.
So I did that (I set a subdomain m.mysite) and on BlueHost I set up the subdomain to
redirect to mysite (this for external compatibility with other code).
If I go to either site mysite, or m.mysite from a browser on a computer or iPad, I can see the site nicely.
However, if I try to login it no longer recognizes me.
So I can no longer edit my site and get it set up correctly.

Any suggestions about how to recover the ability to edit the site?