If facility is 100% negative when will it reopen?

Your mom’s ALF being 100% negative would be wonderful but just a moment in time. When it’s opened up the first person who comes in with their asymptomatic yet infected self can infect their loved one and then the virus is spreading. Or a health care worker can come in and spread it. The fewer people who enter, the better protected the residents are from the virus.
Another poster dealing with Texas prompted me to check on Houston’s numbers today. They have had 125 deaths and 27 came from nursing homes.
Texas is nowhere near a safe zone from the pandemic and especially for those over 65 with underlying issues. In fact the report said a 60 yr old white woman recently died who had no underlying issues.
Houston is one of the largest cities in the nation and your mom may be in a much less populated area. If it were my mom I wouldn’t be pushing for them to reopen until all the health professionals said it was safe and the numbers proved it. But it’s a tough call.

I wonder if all visitors would be willing to quarantine themselves for two weeks before visiting when it does open up?

Here is an article from the Texas Tribune on NH and ALF cases, deaths and recoveries in Texas.

https://www.google.com/amp/s/www.texastribune.org/2020/05/15/texas-coronavirus-nursing-homes-long-term-care-facilities/amp/

All has to do with your Govenor if he has given local jurisdictions the authority to reopen.

Oh, and whats 100% one day may not be the next day. I don't think facilities will reopen until numbers show the virus has died off. Meaning no more new cases.

That is something each jurisdiction will be deciding differently. The fact that a facility is 100% negative has nothing to do with reopening though, facilities aren't closed to keep covid in facilities are closed to keep covid out - if the district surrounding the facility was 100% negative it might have some relevance.