i spend about a day or two dealing with the rental matters (and about 12 days on personal/fun).

That indicates that the *PRIMARY* purpose of the travel is *NOT* for rental management purposes. Therefore the travel is not deductible. But any expenses incurred *directly* related to the rental may be. For example, car rental or other transportation expense incurred for the two days you were directly involved in the rental if transportation was needed from your hotel to the rental property.

Note that I was specifically advised that by establishing in my house in the USA a small home office for managing my rental property,

Unfortunately, you may have been advised incorrectly. A home office for long term residential rental real estate reported on SCH E is not allowed and never has been.