When I can’t pray verbally, can it be done mentally?

Purely mental meditation and communication directed to G-d definitely should have its time and place in every person’s life, and this is very dependent on the circumstances, time and place, etc. Rest assured that G-d is fully aware of all our thoughts at all times! So you should NOT stop meditating about and mentally praying to the One True G-d, but you should also look for opportunities of privacy when, if you have needs that you wish to pray for, you can verbalize your prayers.

You can also spend some of your time mentally reviewing what you are learning about the Noahide Commandments, Torah subjects in general, and your understanding of G-d. This means figuring out what you think you understand, what you don’t understand, how the concepts fit together, what your questions are, etc. You’ll discover what questions you need to ask, and you’ll deepen your understanding. In particular, you can read the Chassidic Discourses that are posted on www.asknoah.org, and then review them mentally and meditate on their meanings as your time allows.