It would be more respectful to arrive Tuesday after dark after the conclusion of Rosh Hashanah, the Jewish New Year.
I would advise visiting after 9pm Saturday September 28, to ask for a Blessing. Yes you can visit anytime, but it is not normal to visit in the Holiday, best before, or after...
B"H The office will be closed. And any Jewish person would not be working there during the day, I believe. But I do believe that they will open soon after Rosh HaShana (Jewish New Year) will end on the night of October 1st. And the cemetery itself is probably open all the time. Hope this helps Ksiva VeHasima Tova!
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