I visited Hotel Karlo mid-February 2017. I'm a 35-year old blond American (very rare in Cali), and I stayed by myself. I never felt unsafe at the hotel. (note - cali is relatively safe for tourists as long as you don't pull out your cell phone or fancy camera, don't flash cash, don't wear flashy jewelry, etc.). Best for people who don't want to spend a lot, but also not interested in hostels. Definitely worth the daily rate.
I knew very little about Cali or Colombia before my visit and speak VERY little Spanish. The hotel is clean, staff are VERY helpful and friendly. A few are fluent in English, so I never had an issue getting what I needed. Staff also helped me find a place to get my nails done, helped me buy a cell phone after mine got wet and ruined (thank you Tatiana!), make international calls, and more.
The best part of the hotel are the staff - especially Tatiana (day) and Freddie (night)! They are truly special people. Hotel is very close to many restaurants and shops. While here, I recommend the neighborhood, San Antonio (10 min taxi ride), with it's hip murals, coffee shops, dance studios, etc. I also recommend checking out the salsa bars.