'go' in plot means plot green circles at the data points with no lines connecting the data points. I don't know if you want the word "go" or if you want green circles. I don't know why you'd want the word go near every data point but if you do, follow Mischa's code. But the "1 unit length from (-1,-1)" is the thing I'm confused about. What does that mean? Do you want a scale bar in your plot, like a "micron bar" they use in microscopy images?
Your filter will select only those data points that fit in the box from -2 to 0 in the y direction and from -2 to 0 in the x direction. But you're using the wrong syntax. You need to do:
filterLogicalIndexes = -2<y & y<0 & -2<x & x < 0;
plot(x(filterLogicalIndexes ),y(filterLogicalIndexes ),'go', 'MarkerSize', 10, 'LineWidth', 2);
