So, for our purposes, I will turn all of his "Spanish" into "Welsh", and "Mexico" into "Wales" ... clever or what !?
Well, for a start, his chapter isn't called "Learning Welsh" ... it's called "Speaking Welsh" which is an interesting choice. It's an attitude. He's writing specifically for people who are going to go to Wales, and at some point will probably want to say things in Welsh.
Right at the start he talks about a couple who went to Wales ... the woman had a degree in Welsh, and her boyfriend knew several obscenities and no grammar - good whorehouse* Welsh. Within a few days she realised that her formal Welsh was pretty useless, largely because she couldn't work out what the hell the locals were saying, whereas her young man was right in there, waving his arms around, laughing , gesticulating over this and that, throwing an occasional inappropriate obscenity and generally making himself understood and liked.
Of course, he is exaggerating for effect a bit there, but we know what he means.... so he goes on to say that you need some vocabulary, and to a lesser extent grammar .... you can gesticulate all you like, stand on your head, but if you want half a cucumber , you'll prefer to know the word rather than relying on sign language and demonstrations.
What he doesn't say explicitly, but implies in various ways, is that a lot of conversational exchanges are mainly set phrases and expressions, repetitions, echoing, hesitations, meaningless interjections .... you know the sort of thing. Basically, you can get by in a conversation with a remarkably small vocabulary and grammar, as long as you have some vague idea of what they are talking about ... and often not even that.
Here's a little section from Waiting For Godot ...
ESTRAGON:Charming spot. Let's go.
VLADIMIR:We can't.
ESTRAGON:Why not?
VLADIMIR:We're waiting for Godot.
ESTRAGON:. Ah! ...... You're sure it was here?
VLADIMIR:What?
ESTRAGON:That we were to wait.
VLADIMIR:He said by the tree. Do you see any others?
ESTRAGON:What is it?
VLADIMIR:I don't know. A willow.
ESTRAGON:Where are the leaves?
VLADIMIR:It must be dead.
ESTRAGON:No more weeping.
VLADIMIR:Or perhaps it's not the season.
ESTRAGON:Looks to me more like a bush.
VLADIMIR:A shrub.
ESTRAGON:A bush.
VLADIMIR:A—. What are you insinuating? That we've come to the wrong place?ESTRAGON:He should be here.
VLADIMIR:He didn't say for sure he'd come.
ESTRAGON:And if he doesn't come?
VLADIMIR:We'll come back tomorrow.
ESTRAGON:And then the day after tomorrow.
VLADIMIR:Possibly.
ESTRAGON:And so on.
VLADIMIR:The point is--
ESTRAGON:Until he comes.
VLADIMIR:You're merciless.
ESTRAGON:We came here yesterday.
VLADIMIR:Ah no, there you're mistaken.
ESTRAGON:What did we do yesterday?
VLADIMIR:What did we do yesterday?
ESTRAGON:Yes.
VLADIMIR:Why . . . Nothing is certain when you're about.
ESTRAGON: In my opinion we were here.
VLADIMIR: You recognize the place?
ESTRAGON:I didn't say that.
VLADIMIR:Well?
ESTRAGON:That makes no difference.
VLADIMIR:All the same . . . that tree . . .that bog . .
ESTRAGON:You're sure it was this evening?
VLADIMIR:What?
ESTRAGON:That we were to wait.
VLADIMIR:He said Saturday..... I think.
ESTRAGON:You think.
VLADIMIR:I must have made a note of it.
ESTRAGON:But what Saturday? And is it Saturday? Is it not rather Sunday? ... Or Monday? ........ Or Friday?
VLADIMIR: It's not possible!
ESTRAGON:Or Thursday?
VLADIMIR:What'll we do?
Look at all the repetitions, the very short bits, sometimes just one word, the questions, the stock phrases ( it's not possible, you think, possibly, and so on, let's go ) ... at many points in that dialogue, the speaker has a huge choice of what to say, and often avoids answering properly in a variety of ways. Conversations often go like that, and you can get by with a surprisingly small battery of words and phrases without revealing your lack of fluency.
It reminds me of David Crystal's remark about how you judge someone's knowledge of a language for practical purposes ... and basically, the best and easiest quick measure is simply the number of words they know. Simple as.
Incidentally, David Crystal's interest in language was largely triggered by his Holyhead upbringing, where he came into contact with a lot of Welsh speakers.
So ... having a mental collection of useful words, phrases, interjections, questions, ways to get a sentence started or finished, tags etc can be a great boost to your "conversational confidence"....
But now, the musicians are waiting nervously in the wings, the lights have dimmed, and the audience waits expectantly ... and then top Welsh band Messner take the stage and their first "number" is Golygu Pam ....