Can I go to the er/urgent care with concern of lump in my breast?

[Emmasearson]

Last week I was giving my self a breast examination whilst in the shower. When examining my left breast I found a walnut sized lump  on the left side of left breast. I had my husband come in a feel it, he said that he had not felt it before either.
The next day I made an appointment at the women's wellness clinic at harbor ucla medical center.
The next day I went for my appointment and saw the nurse practioner. She felt the lump and said she was referring me to a diagnostic mammogram and breast ultrasound. This was instead of a regular mammogram.
2 days later I received a call from them for my scheduled appointment. The date she called was 06/25/18. There 1st available appointment isn't until 09/11/18. I asked if that was because it wasn't anything to worry about, and it wouldn't make any difference to put it off for that long? She answered oh no I'm not saying it's not urgent, its just that this is the 1st appointment available.
Well I am homeless, i live in my van, and don't have insurance st the moment. So I'm stuck because I cannot just go and pay somewhere else.
So my real question is.
If I go to the harbor ucla medical center hospital ER/URGENT CARE. Can they do anything else for me other than waiting for 2 1/2months for my original appointment.
Would I be foolish go wait that long?