Is there a pre-publication access for ACM journals?
My experience with ACM Transactions publications, as both author and editor, is that they do not generally offer any sort of early access.  

I find this rather strange for a computing society, but suspect this may be because they also have fairly liberal preprint policies: authors can put early versions of their article up on arXiv or similar repositories.  Many ACM journal articles are also extended versions of conference articles, so that is another route for accessing information that you may be looking for.