How to shoot 30fps with Canon 5DMk3?

I can only see 1920 25 All-I, 1920 25 IPB, 1920 24 All-l, 1920 24 IBP, 1280 50 All-i, 1280 50 IBP and 640 25 IPB.

In the manual it says I can shoot both 30 and 60, but I can´t find it. Where is it?

Ahh, I just found it.
Had to change to NTSC. What´s the different between NTSC and PAL when I mix those two?

Can I have some clips with 24fps(PAL) and some with 30fps(NTSC)?

Yeah, change to NTSC.

The difference between PAL & NTSC is just the framerate. If you are going to be delivering for Broadcast then it matters - NTSC for North America (and a few South America countries) and Japan mainly I think, PAL & Secam for the rest of the world.

Most PAL dvd payers (and TVs) are able to play NTSC discs, but not necessarily vice-versa.

Basically, the first clip you drop into the timeline on FCPX will determine the project settings (or you can set them manually). So if you drop in a 25p clip - then thats your framerate. If you drop in different framrates then those clips will be conformed to 25p (it might cause some small issues in speed and maybe synch - never tried it).

Generally its best practice to try and have a standard framerate. The exception is when you want to do slow motion - in which case you film in 50p (for a 25p timeline) or 60p (for a 30p timeline) - when the framerate is conformed it causes a slow motion effect (which its usually further slowed then by Twixtor or Optical Flow).

Great answer!

So, if I made a movie with 24fps(PAL), it can`t be broadcastet in the states?
Just because of the frame rate?

Ahh, so I need to decide what frame rate my movie is going to be in?
I thought it would be handy mixing frame rates in vacation footages, but if FCPX conformes the clip to my first frame rate, it`s useless to change the frame rate?

PAL video can be broadcast in the States; it happens all the time with BBC stuff for instance (usually that is 50i interlaced too, not 25p). However it has to go through all sorts of post work to make it happen (and make sure it looks right). Bear in mind most broadcast is still often interlaced.

Basically just choose the framerate that suits the country you are in. PAL is correct for Europe -traditionally 50i, but more commonly 25p these days.

Since it used to do it a lot, I have Compressor custom presets I've created to go back and forth from NTSC to PAL, that I've recently added to my FCPX's Share menu. A tad off the topic, but just FYI.