The winner is: With whom am I speaking? You wouldn't say, "The car am I driving in?". And you should avoid dangling prepositions. If your sentence (or clause) ends in a preposition, it is either extraneous, or your sentence requires rewording.
Terminal prepositions are poor Latin , but they are perfectly acceptable English . The prejudice against terminal prepositions (and split infinitives, as well as such abominations as the s in island) came from a period in English linguistics where a bunch of grammarians thought that English wasn't dignified enough, and tried to pretend that it was a Romance language by shoehorning the language into awkward and ungain…
I watched a series of college lectures on the history of language a couple of years ago, and that was one of the main points the lecturer made. Growing up in a traditional school system, I had never really thought about it that way.
Having said that, there is also a "high" and "low" version of most languages. The "high" version is full of obtuse rules and associated behaviors, while the "low" version is more catch-as-catch can.
So yes, you are correct: enjoy the art of your native tongue! I love screwing around with the rules. But also be aware that the culture you are in may prescribe all sorts of silly little rules, and knowing these -- and when to apply them -- can drastically affect other people's perception of your character. Whether we like that fact or not.
One of the things I wish I had more time for is the study of languages and the philosophy of languages. It has direct application in everything from AI to talking to Dolphins to programming projects. Really cool stuff.