Is it safe to jailbreak an iPhone?

I heard your iPhone will crash or have bad signals and such.

Supposedly it's legal to jailbreak it. But depending on what you get affects the phone since it wasn't approved by apple. And plus if you break it apple will refuse to fix it.

Jailbreaking won't affect your signal. If you do it wrong you could brick (ruin) your phone. And you won't get any customer support from Apple anymore if they find out you jailbreak it. Jailbreaking is NOT illegal; switching your device from your current carrier to another carrier is illegal.