Searching for Journal acceptance/rejection rates at times can be difficult. Try the following.
Some jounals will have the rate in the "information for authors" area of the print journal or on the WEB homepages of the journal.
Most societies will include the information on their WEB home pages.
Do a Google search = "acceptance rate" or "rejection rate" and "discipline" (not all journals will be found)
Contact the editor of the journal and ask. Some do and some don't furnish the information.
Look in "Cabells Directories of Publishing Opportunites" (UTEP faculty, students, and staff)