Many girls are pretty and they would be potentially interested in foreigners but the social pressure from men and society at large is strong.
It's very uncomfortable to have dates in bars and restaurants (Ethiopian men will stare at your girlfriend as if she were a working girl, whether she's one or not). It is a pain to be in public anywhere with an Ethiopian girl when you're white.
This is a primitive culture in that sense: They don't like foreigners dating their women and they will make you feel it: their territory, their women. The whole scene is depressing.
As far as mongering is concerned, it is really bad as well. During the day there is no option (only massage parlors with at best a HJ)
At night there are only very low quality girls in the streets, some are pretty but it's not hygienic at all.
There are little bars (Christmas lights) in Chechnya (Mike Leyland road, close to hotel Atlas) and other places but again the hygiene standards are very low (those girls take a shower a week maybe) and the area is not safe.(There are also usually no rooms in these bars). However, these girls are usually prettier than the ones in the nightclubs but with less education (almost no English)
Then you have nightclubs like Concorde or Memo (opening at 11:30pm) where girls will ask you around 600-1'000 birrs to go back to your place. I have never seen a very pretty girl in these clubs (maximum rating: 6-7 out of 10). Not worth it.
Then you have Ethiopian dirty low class clubs in the street going up on the left of Hotel Taitu, in Piazza: you will not feel welcome as a foreigner in these clubs and the girls are low class. Some of them are pretty and there are rooms in some of the clubs but no shower. Again big hygiene problems there.
In conclusion, if you like low class cheap dirty (pretty) street hookers, then Ethiopia is for you. Otherwise, go somewhere else.
There is also no party atmosphere like in other African countries and pro girls in night clubs are not better looking in my opinion: their faces are nicer than Sub-Saharian African girls but they usually don't have very good bodies.
It is a very tight-knit, closed society where as a white man you will have a very hard time to have fun, let alone integrate (it's much more closed than other African countries)