I am a first year combined internal medicine-psychiatry resident currently doing inpatient psychiatry. We (myself and other interns) have had patients who speak anything from Spanish to Vietnamese to Polish as well as other languages. Although it is ideal to have a physician who can speak the patient's primary language that is often not the case and interpretors are used. It potentially can be a bit more awkward or difficult discussing mental health issues through an interpretor, however, patients are often so relieved that someone is addressing the issue that they don't seem to care. I also think that most of the awkwardness is something that we feel (if you were a patient, what is the difference between telling one versus two people about your depression and thoughs of suicide or voices you hear- as long as both people are acting professionally?). What is said through an interpretor remains confidential and patients need to be informed and reminded of that. In my experience, patients seem more comfortable speaking their primary language and having an interpretor present than the alternatives. The interpretor can also clue you in to certain cultural differences.

As for going to other countries when disaster strikes. I do think that there is a role for mental health care workers, including psychiatrists. One thing to keep in mind, however, is that most people immediately after an event are in shock or denial and are dealing with the bottom of Maslov's hierarchy of needs (food, water, shelter, etc.). There are often normal grief reactions that may need counseling (often better provided by crisis counselors or mental health social workers). Much of the psychiatric stuff doesn't come until later.

You sound like someone who might be interested in Doctors without Borders (Medicins sans Frontiers).

Hope this helps!