Don't be intimidated by anything or anyone. There are strange people everywhere, it's just that in church we always notice them more because we're in a house of God where we want to feel love and unity. Anything that falls short of that jumps out like a sore thumb in comparison to other places. Most importantly understand that you're going to God's house, not to a social arena. We are all there because we need to be with God together.
It may be a surprise to you, I was raised Orthodox from the cradle and when I visit other ethnic parishes where I don't understand the language and don't know anyone, it's not easy for me either. I feel like a newbie.
There are, for example, small yet noticeable differences in tradition. Russian priests expect the faithful to approach them for a blessing, but they all will shake your hand too, esp. if you're not Orthodox. Other priests don't usually do the blessing at all, Serbs usually don't, neither do Romanians, with Greeks only bishops do it, etc. Also, Serbs kiss their candles when they put them up, Russians don't. Other Orthodox have a tradition of lighting a candle and then approaching the candlestand with an already lit candle. Russians don't do that. Many Orthodox cross themselves at clergy when being censed at by the priest or deacon. Russians don't cross themselves at clergy because, as the clergy say, "we are not icons". Some people kneel on Sundays, Russians as a rule don't do that because Sunday is considered a celebratory of the ressurection. Then in one church recently I was barred from putting up a candle during the reading of the hours and during the first part of the liturgy. I've never seen that anywhere else - as a matter of fact one would usually argue that this is THE BEST time to put up candles. Things like this can throw me off when I go from place to place!!
Also, some churches are particularly newbie friendly (and ALL churches SHOULD be like this). Others are full of older people from an ethnic community who've known each other for years, who probably built that parish together, and may be somewhat cautious about new people coming in (and to be fair to them, there are many horror stories of new faces coming in who try to take over the parish, etc). I know of such parishes where it will take months for people to warm up to a new person and cut them into their social circle. That's wrong imho, but it does happen.
Go to the place where you feel most comfortable. Stand in the back, so you don't feel intimidated. You can come up to kiss the cross at the end of the service and recieve the antidoron (bread), but sacraments such as communion are for those who are already accepted into Orthodoxy (baptized/chrismated) and have prepared. If the service is in a foreign tongue, ask for a service book in English. Even if the service is in English, it's a good idea to have it anyway, it helps you follow along and make sure you don't miss anything.
If you can't stand for the whole two hours don't feel bad about it. Go for fifteen, twenty minutes for a start. Show up for the beginning, it's a little less crowded then - although the time to meet people is after service. Often after liturgy they serve memorial services for the deceased, so it may take a while for the priest to be free and meet you.