First of all, thank you for your concern. It is people like you that will keep America's pride in check. It is great that your neighbors want to show respect and pride for their country, however, equal respect should be shown to the American flag. If they wish to only fly their country’s flag, well then I suggest they return to their country. They must realize that they have made America their home, and therefore must submit to the country’s rules. It is fine if they do not want to show American pride, but they should not by all means show disrespect. Simply they either display both flags or no flag at all. If they do decide to display both flags, they should not fly on the same rod. Instead, both flags get their own rod, but must be approximately equal in size and flown at the same height. Flying one flag higher than the other is disrespectful to the other country, even if it is not our country. This is significant to show that America is at a time of peace with the other country. Please be sure to let neighbors realize that America is respectful of other countries, but citizens do have proper conduct to maintain.
I hope you have a great day, and good luck with your neighbors!