It will be very difficult to change into CS at UCSD or Washington, so attending either would not be a good idea if there is a possibility he may want to do CS.
Note that biology tends to have low post-graduation pay levels, so it may only be a good major if he has frugal spending habits and does not have any debt. Bioinformatics or computational biology, if available, may be better (but check if it is difficult to get into that major).
Post-graduation pay of graduates who received federal financial aid, from College Scorecard:
| Major | College | Median Pay |
|---|---|---|
| Computer Science | UCSD | $86,972 |
| Computer Science | Washington | $101,221 |
| Biology | UCSD | $29,805 |
| Biology | Washington | $31,859 |
| Bioinformatics | UCSD | $71,015 |
| Computational Biology | Washington | NA |