Thank you all very much - valeria, manuel, aztlaniano, speedier jsmartin - an impressive array of skill, determination and goodwill. The translation I am working on is about Madrid's ill-starred Olympic bid, and I have finally settled on two terms: "accomodation capacity" where the question is more the number of hotel rooms available, and "visitor reception capacity" where wider concerns are involved, especially environmental ones which are a major issue. However, "aptness"...yes, I will have to stick it into the text and see how it sounds. "Hosting" is used in another sense (after the Candidate City phase we would have had the Host City phase, but now Río de Janeiro will be hosting the games) so that one is ruled out to avoid confusion.