I don't think these are unconditionally a good idea. In places where a minority language was there first, it's good to have a reminder of the region's history (much of Wales is like this, as is most of eastern Turkey, where by and large bilingual signage doesn't happen).

In much of Scotland it's a nonsensical waste of money. It's not like Glasgow Queen Street Station had a traditional Gaelic name before the Sassenachs expropriated the Gaels' railway network. There are Gaelic signs in large parts of Scotland where nobody now living has been part of a traditional Gaelic-speaking community.

If the government wants to promote Gaelic, instead of paying some bureaucrat to think up neologisms to rename features that have always had Scots or English names, their cash would be far better spent on making Gaelic-medium porn movies.

there are probably more people in the UK that can speak Farsi,or Pushtu,or Tagalog,or Hebrew,than can speak Welsh

No there aren't. Urdu has about the same number of speakers, Polish may currently have more (though only a minority of Poles see themselves as permanently resident in the UK). No other immigrant language comes close.

Gaelic can't rank higher than sixth in Scotland - behind English, Scots, Polish, Urdu and Italian, possibly lower than Chinese as well.