Unfortunately, the Hopkins statistic is not currently produced by any procedure in SAS.
PROC MODECLUS performs the saddle test and you can use this to test for unimodality. You need to specify the R= and JOIN options in the MODECLUS statement. METHOD=1 is the most commonly used method and you can find the description here under PROC MODECLUS > Clustering Methods
There is an example in the documentation: Cluster Analysis with Significance Tests
One way to estimate the number of clusters is to run the analysis over a range of values of the smoothing parameter. If you get the same number of clusters over a range of values, then that is a likely indication of the number of clusters. For a more detailed discussion, take a look in the Details section of the MODECLUS chapter, particularly the 'Density Estimation' and 'Significance Tests' sub sections.
For additional discussion and ideas for determining the number of clusters, see "The Number of Clusters".
Hope this helps!
Doug
