I would convert the GRID to ASCII format first using Raster to ASCII (Conversion). If you have many GRIDs, use the batch conversion by right-clicking on the tool and selecting "batch". Then you can easily bring in the ASCII files into MATLAB using
arcgridread. Here's an example from Mathworks:
[Z,R] = arcgridread('MtWashington-ft.grd');
xlabel('x (easting in meters)'); ylabel('y (northing in meters)')
There is also a discussion here that may give you some ideas too.
Another option is to convert your ESRI grids to another format, such as a TIFF, and bring them into MATLAB using