If you can lift the bar, you are strong enough to compete. If you go to a competition and lift you won't be embarrassed no matter how little you lift. I've seen 1000 lb. squatters cheer for people squatting in the 200's if they are trying to grind one out. Your entire goal with your first competition should be to get a total, then you have something to try and beat the next time out. If you wait to get "strong enough" to compete, you will never compete.
Plus the motivation and training information you can pick up at a meet by talking to people can be invaluable.