Were the previous Slayers located on Hellmouths too?

There are lots of Hellmouths within the buffyverse.

From wikipedia:

"Hellmouths are places of increased supernatural energy. According to the mythology of the "Buffyverse", this is the area in which the barriers between dimensions are weak. The Hellmouth has a focal point, which serves as a portal between earth and Hell. For these reasons, the Hellmouth attracts demons and other supernatural creatures, becoming a "hot spot" for supernatural activity. The television series has confirmed that there are Hellmouths under Sunnydale, California and Cleveland, Ohio, as well as other unspecified cities around the world (cf. "Chosen")."

So it is possible that these past Slayers where guarding another "hot spot" for supernatural activity.

We will never know. I never assumed they were on hellmouths, though it would make sense. We know from episodes of buffy that there is another hellmouth in ohio. If I take what I know from the series, the slayer that Spike killed in china, was during a rebellion. Maybe the demons were drawn toward the conflict and violence, and the slayer followed. The other slayer that we know of, Nikki Wood, lived in New York, which is a high crime, high population area. I assume the vampires would be drawn there because of the easy pickings.

As it is seen in the show, when the Hellmouth becomes more unstable, increasingly active as it is shown at several instances during the life of the show, "evil" becomes more agitated if you will. Season 7, the Hellmouth was bursting at the seems and the kids were practically ripping each other apart.

So demons, vampires and other baddies roam the earth in the shadows and some like bugs to light eventually make their way to the Hellmouth and/or the Slayer gaurding it. Of course not all the bad guys have a profound interest in persuing either.

The Question at hand, based solely on the series, seems as such. Yes there are other Hellmouth's. I personally feel as though the Council nudged Buffy and Joyce to sunnydale somehow to guard the Hellmouth.

(I am actually watching one of my fav ep's right now, Passion. So if this is hard to follow, my apologies. lol)