Is the Native Experimental Hostel in a Safe area for walking at night to bars etc?
I don't know what you're comfortable with. I don't consider anything in that area actually dangerous, but I have a somewhat different perspective. But the hostel is kind of by itself, by the rail tracks and across from major highway overpasses, backing onto a fenced scrap metal yard. Might be some homeless settled in under the overpasses. If you walk north on that side of the highway, it's very open ground. No place for anyone to lurk. But probably no one else walking until you get near 6th Street. And if you turn west under the highway on 6th or 7th, you're into the bar district and lots of traffic. At any reasonable time of night, there should be enough vehicle traffic that you won't be wholly alone on the street.
I have heard that newly opened Native Hostel has a really cool vibe. It is right off I-35 between 3rd and 4th Street. There is a bicycle\walking path that links the east side of I-35 with the west side, under the I-35 overpass at 4th Street. Use the 4th street path instead of the larger 6th\7th underpass, there are a lot of homeless and panhandlers there. I use the 4th street path on a daily basis during daylight, and have always felt perfectly safe. I would imagine that it would be safe at night as well. Just use common sense safety as you would in any large city and you should be fine..
Staying at the Native Hostel, you will be really close to some awesome night spots on the east side.
If you're comfortable in some of the more iffy areas in NY, Boston, Baltimore etc and you're a healthy, fit male perhaps the hostel will work for you. I wouldn't recommend walking in that area at night unless you're in a group. I don't recommend it for a female visitor.
That particular pocket of Austin will improve significantly when the Fairmount opens at Cesar Chavez and Red River.
Welcome to Austin!