Here's another must have tweak for jailbroken devices. With NotesFont you can change size and font style in the native Notes. There's a bunch of new and amazing fonts can be found in the tweak.
posted here to jailbreak your iPhone using Limera1n. Once your iPhone is jailbroken, tap on Cydia and search for NotesFont under BigBoss repository for $0.99 then install it. Once installed, navigate to the Settings app and touch NotesFont option then choose your favorite font. Well done!