Although it sounds counter intuitive if the dollar is devalued it means it buys less. Has the same effect as inflation in that the price of goods rise because the dollar value is less.

Dollar devaluation or inflation, the end result is the same. It can be devalued by printing money.

It can devalue against different things. If it devalues in relationship to other currencies the price pressure will be in imported goods. If it devalues against commodities then the prices of commodities go up. 

John