[greenyoda]

Given a choice between those two, I'd recommend algorithms, since you can probably apply that knowledge more readily to everyday programming projects. For example, it's useful to know roughly how long it takes to sort an array, add an element to a hash table (like a Python dictionary), etc.

Language theory probably won't be that useful unless you're planning to write a parser for a programming language or something similar. I occasionally need to deal with grammars (for the Bison parser generator) in the work that I do, but most people probably do that kind of thing very rarely, if at all.

Also, it's never too late to learn stuff.