Ships will warp between planets in the same system if time is an issue. For example, this was an option available to Captain Kirk when he had to ferry the Dohlman of Elas to Troyius.
Here is the relevant dialogue:
KIRK: Mister Chekov, lay in a course for Troyius. Mister Sulu, impulse drive, speed factor point zero three seven.
SULU: Impulse drive, captain?
KIRK: Yes, that's correct, Mister Sulu. Sublight factor point zero three seven.
SULU: Aye, aye, sir.
SCOTT: Captain? You'll not will be using warp drive? All the way on impulse. That'll take a great deal of time.
KIRK: You in a hurry, Mister Scott?