Lower levels it'll more often be mismatched because of smurfing and a lower player pool (matchmaking will have to widen its search to less appropriate players). However, it's still better than no MMR; it's there so it at least tries to get you with players around your skill level. This will be better at level 30 I assure you.
If PvP is not quite your thing yet, I do recommend playing Co-op vs. AI; while you won't get a highly competitive experience, you can still use it to learn how to build and play your champions. I myself farmed vs. AI to level to 30, and continued afterwards to learn about what every champ was capable of as I earned IP to buy them and buy Runes/Pages to prepare for Ranked play (Rune system is going away in the preseason, though).