Is probably your best bet. Many providers do post tour cities and dates there. If you follow girls you like, you may get your answer thru notifications. I know two ladies who visit my city once a year who I like to see, and I’m aware of the months they like to come, so sticking with ladies you like helps to know when they visit your city. They often send messages via P411, or E mail to clients they have met in the past when planning to visit a city again.

Agencies often post tour cities and dates, but I like my independent girls. P411 allows you to do advanced searches also and you can search for visiting ads. That is about as one stop shop as you can get. I do like to keep an eye on my TER local ad board too. Most girls post ads up to a month before visiting a city.

Yeah, Thanks, I do all that now, but it takes a better part of a day just to find 1 or 2 that will be in the city I will be in on the same dates.

Not looking for my home city but the cities I'm visiting.

I guess you are trying to match up with touring ladies. Sounds way too freaking complicated to me. P4P is supposed to make my life simpler.
I have been lucky that some of my trips have coincided with one or two. But there are so many wonderful local women in the cities I go to, that it just doesn't make sense to add more stress.

Start one

It has been suggested that TER add a calendar to do what you suggest.  See, e.g.,  
http://www.theeroticreview.com/discussion-boards/suggestion-and-policy-4/a-ter-calendar-feature-16002?page=1
.
I think it can be done using minimal resources and open source calendar / scheduling software.  Keeping it limited to -1 day to +10 days or -1 day to +14 days saves resources (storage and computing = searching).

I agree, twitter would be you're best option. I'm a new provider and I see so many providers from all over the world post their tour dates on a daily bases.