An ampersand ("&") is outputted as HTML encoding ("& amp ;")

Fixed in the development version (1.6.3-alpha):

https://github.com/scribu/wp-query-multiple-taxonomies/commit/3f053bfcd2c3b6a7be0bd60e71515cc08f983c0d

That was fast, great. Thank you.

PS: Just to make sure you didn’t miss it, I’ve checked and encoding issue occurs not only in dropdowns mode, but also in lists and checkboxes mode.

Fixed those too: https://github.com/scribu/wp-query-multiple-taxonomies/commit/99e150961ecffb9999d888626dbdf19486f31290

Thanks for reporting.

Thanks for your solution.