Hi Tom -
First, this model is not identified. As you have it, individual attributes affect the utility of all choices to the same degree (ie simply result in a shift in utility for all choices that does not change their rank ordering). Your beta needs to be a matrix (probably with the P-1 parameterization, which can be achieved by setting the last row as 0).
Second, it assumes that all individuals the same marginal utilities, and so you’ll get the red bus/blue bus problem. That mightn’t be a concern for you.
Third, with logits, normal(0, 5) is an enormously wide prior.
Hope this helps!