The questions are "safe for whom and from what?"

Safe for a provider?  Obviously LE is the primary concern.  Unfortunately, I doubt that there are many, if any places for a provider wanting to post her number, rates and photos, that a LE agency wanting to do something about the "prostitution problem" don't know about.  Of course, careful screening can mitigate this.

For Clients?  LE is also a risk, but careful research will minimize this.  Other risks are "is she the real deal, and are the pictures real."  Again research is the key.

As to where to advertise, there are 2 main national escort malls, eros.com and cityvibe.com.  From what I've experienced eros is a step above Craig's List, but has more than its share of fakes and rip-offs.  I see that a number of my favorite ladies I've seen, or want to see, advertise on Cityvibe, which tells me it is a bit more reliable, but I would never see anyone on a Cityvibe ad alone.

Of course it all depends on where you are located.  Here is a link to the best ad site I know of.  It is run by an active TER member.  If only every site were so selective in allowing advertisers to use their site!!!