Better to do both!!
If you're going to learn 'a few tunes' to practice the patterns, the most beneficial way to do it would be to do it in all the keys and in all the registers - scales are actually a shortcut to this since you (should) play from the bottom to the top of the instrument and back in all keys. This necessarily means that your fingers can find the adjacent notes in whatever key you're playing in, at whatever pitch.
Throw in arpeggios in all keys and you've got all the 3rds and 4ths too (which are a bit like 5ths and 6ths upside down).
Don't mean to 'shoot you down'
but it's hard graft that really pays off. I recommend to the kids I teach that they do a 'five minute plan' of scales as a warmup each time they practice, and then they can forget about them for the rest of the session.
Choose five scales, spend a minute on each, and mark them according to your success rate - move on from 'perfect's and 'good's, and work on the 'messy' and 'don't know's again tomorrow.
Oh, and you will find that melodies use scales, or they wouldn't be melodies..! ;}
Nick