Phone or Skype interviews can be as valuable as in-person interviews. You shouldn't dismiss these or think of them as less. Often, these are the only option you have to chat with selection committee members. Sometimes they are not "true" interviews - they might simply be a nice chat with a faculty member or the internship/program director at a private practice program.
Even if certain programs offer in person interviews or visits, you might not be able to go. It is expensive to travel, and time off is difficult to come by! Airfare plus accommodation on an intern/resident salary is hard to manage, especially if you're going to multiple places. Check the program descriptions to see what type of interviews (if any) a program offers. If it only mentions in-person interviews, it is ok to ask about phone or Skype options. People in charge of the internship and residency programs understand that you're most likely on a limited budget, both with time and money. The worst they can say is no.
However, if it clearly says no interviews are offered, you have little to gain from asking. You might end up being perceived as someone that didn't even bother reading the program description (if you read our posts, you know by now how important it is to do so!).
Bottom line, regardless of the type of interview, it is always supposed to be a conversation! Do some research, anticipate the usual questions, be yourself, stay calm (as much as possible) and answer questions clearly. You'll do just fine - good luck!