Is it okay to to get 2 liter bolus of normal saline IV fluids several days in a row for severe diarrhea when labs show no dehydration? We don't know the cause of diarrhea yet.

Yes. I presume normal kidney function.Our body is capable of dealing with a great deal of intervention.I'd suggest the dr's giving the fluid are watching very closely what is happening.
Yes. Dehydration may be clinically evident to your treating physician, and replacing electrolytes may be necessary without your being dehydrated. Sounds as if you are being appropriately evaluated. Stick with it and hope you are better soon.