No, the inflation rate on their fiat would go on normally, because adopting bitcoin doesn't magically make the peso "strong". But of course listing things in bitcoin price will make it look that way if you ignore the peso price going up and the bitcoin price going down on the same item.
In a way, it would halt the inflation, because its like telling people to start using gold coins from now on. Argentina can have dual coins, like Peru with the USD, or get rid of the peso entirely but that would probably cause more confusion at first than simply letting both be used for a transitional period at least.
To adopt a "strong" currency (ie. like gold) adopting Austrian economics is a must. You have to get rid of debt asap and force banks to adopt 100% reserve system, and close the central bank because you won't need it anymore. If you only adopt the "strong" currency but keep the rest intact, you might be getting in a worse situation similar to what happened in the 2000ies, because that's was Chicago economics, the one socialists mistakenly call "neo-liberal", Ie. Friedman et al (Growth by debt, instead of growth by "true" accumulation).