Language

"de la capell" sounds like Catalan to me. "of the chapell".

"Ex voto" is Latin, and is used both in Spanish and Catalan. It means "promised offering for a favor received".

So probably the donor of the statue promised to pay for it in exchange for some favor (usually, recovering from an illness).

The "des" in the phrase is what I don't understand.

BTW, welcome to A2K

Re: Language

I too looked at the words thinking they looked like a mixture of three languages at first glance. But here is a thought - though I do not know how it will resolve "des":
Many Saints are given special appellations in their native land, which are often taken over into other tongues with as little adaptation as possible. Think of all of the words from "St." to "Capell" as a single name, having nothing nescessarily to do with the language of the whole line, and what remains as the line's tongue into which the name is a strnge ingrafting. Perhaps?

As fbaezer pointed out it's just plain Catalan:

"St Joseph of the ex-voto's chapell"

In French: St Joseph de la chapelle des ex-voto.

fbaezer - the word "des" translates as "de los" in Spanish.

In modern Catalan, it would read "dels".
"des" is French, isn't it?

Yes, it is, but also Catalan as it's not a unified language and it differs from place to place.

So, in some places "dels" is "des" as I've often heard.

Catalan stretches from South of France to Catalunya and Valencia region, Baleares, Sardinia, Andorra...