Libertarians have a fortress America point of view and want us to have the foreign policy of Switzerland. They essentially want America to keep to ourselves and not meddle in the affairs of any other nation and not be involved in wars. Ron Paul articulates this position pretty well. I personally disagree with this view but it is a view held by many of the founders. On economic issues and especially sending the libertarians are right on which is why if you heard Ron Paul he makes all the sense in the world on fiscal issues.
Libertarians are also pretty much open border types which is another issue conservatives disagree with them on. They are also pro-choice and very liberal on social issues. I would describe them as conservatives that are liberal on social issue and want a foreign policy like Switzerland.
Wow, rather refreshing to see someone disagree without labeling the other party (esp Paul) names.
As you pointed out, many Founders warned against foreign entanglements.