Half my family is Catholic and I have been to Catholic Mass times as a kid and as an adult. I would attend mass for years with my grandma as a kid. If you lived near me I am sure my family would give you a warm welcome and introduce you to mass.
The catholic Church my family goes to is right across the street from our Masonic Lodge, so this makes it much easier for me if the church is having an event at the same time something is going on at our lodge.
Many Catholics let friends or family take the Eucharist, my family encourages me to do it. If you don’t take the breed you will stick out like a sore thumb and not blend in, so I recommend taking it. From my experience this won’t offend most Catholics and no one will know anyway.
I would also make sure you practice making the cross before you go just so you blend in better.
You can’t take communion. You are not Catholic.
The guidelines for receiving Communion, which are issued by the U.S. bishops and published in many missalettes, explain, "We welcome our fellow Christians to this celebration of the Eucharist as our brothers and sisters. We pray that our common baptism and the action of the Holy Spirit in this Eucharist will draw us closer to one another and begin to dispel the sad divisions which separate us. We pray that these will lessen and finally disappear, in keeping with Christ’s prayer for us ‘that they may all be one’ (John 17:21).
"Because Catholics believe that the celebration of the Eucharist is a sign of the reality of the oneness of faith, life, and worship, members of those churches with whom we are not yet fully united are ordinarily not admitted to Communion. Eucharistic sharing in exceptional circumstances by other Christians requires permission according to the directives of the diocesan bishop and the provisions of canon law. . . . "
Scripture is clear that partaking of the Eucharist is among the highest signs of Christian unity: “Because there is one bread, we who are many are one body, for we all partake of the one bread” (1 Cor. 10:17). For this reason, it is normally impossible for non-Catholic Christians to receive Holy Communion, for to do so would be to proclaim a unity to exist that, regrettably, does not.
Another reason that many non-Catholics may not ordinarily receive Communion is for their own protection, since many reject the doctrine of the Real Presence of Christ in the Eucharist. Scripture warns that it is very dangerous for one not believing in the Real Presence to receive Communion: “For any one who eats and drinks without discerning the body eats and drinks judgment upon himself. That is why many of you are weak and ill, and some have died” (1 Cor. 11:29–30).
You are free to participate as much as you feel comfortable or to just sit back and watch. Most parishes will have a book called a missal in the pew, or maybe in the back when you walk in. It can be a bit confusing at first, but contains all the responses and prayers during mass.
Taking the Communion if you are not Catholic (not had 1st communion ceremony in a Catholic Church) is serious and considered a sacrelidge! Wanting to blending in and permission from your family does not substitute the right of initiation.