Is it safe to keep passwords saved in Firefox?
If you are the only one who uses your computer and no one can copy your password files. I suppose someone on a public network without a firewall, a hacker could get your password file. You can block outside access even in public places, but that can be cracked over time.
Second level, Firefox use a master password:
Firefox comes with built-in password manager tool which remembers username and passwords for all the websites you visit. This sign-on information is stored in the
encrypted form in Firefox database files residing in user's profile directory. However any body can just launch the password manager from the Firefox browser and view the credentials. Also one can just copy these database files to different machine and view it offline using the tools such as FirePassword.
Hence to protect from such threats, Firefox uses master password to provide enhanced security. By default Firefox does not set the master password. However once you have set the master password, you need to provide it every time to view sign-on credentials. So if you have lost the master password, then you have lost all the stored credentials as well.
Most of the time when people I know have been "hacked" it's because they used the same password everywhere, including email and some site with lax security lost the user records. Hey, Bob's BBS has the same password as PayPal for some people. Come on, it doesn't take a big hacker at the airport to get into that and it also gives, email addresses and passwords, the door is open by the person who can't figure out, they need different passwords for their own security, or a password means nothing.
Easiest way is even if you have the same passwords for Microstock sites, then a different one for email, and something else for PayPal and another one for banking, and maybe another for forums... but never the same password for banking or income as on a forum or email. Lose one, you lost them all. And what someone wrote, many of the password recovery tools are simple enogh to fool. The newer ones ask a question, that you set, but then, who needs that when the passwords are the same on 1001 sites?

I have a notebook. You know, old fashion steno notebook and a pen. I keep my passwords recorded there. If it's that important to have a secure password for On The Road for PayPal, maybe a note card would do it, and that way it's never entered in the computer. Now that's security.
But using a master password on FF should be secure for travel if that's the concern.
Nothing is perfect and 100% safe. NOTHING!