5984 Assessment
Abstract Clear, direct.
Research Question The research question is clear and well defined.  It is, however, perhaps a bit less ambitious than it might be.  
Literature Review  The literature review is clear and effective.  The final version should expand it, but this is a good start.  The references to controlling for SES are sometimes unclear whether this concerns the SES of individuals or that of neighborhoods or school parents.   The review seems to overlook relevant characteristics that are correlated with the "independent variable", such as average school size.

It would help to review some literature on the education system in Puerto Rico and how it differs from the education system in the United States.

Since social capital seems to be an important part of the main hypothesis, a bit more attention to social capital theory might be worthwhile. Note that some authors disagree that strong network ties are automatically beneficial (sometimes close ties prevent a person from seeking outside opportunities).
Data The data described in the draft proposal seem on target for the research agenda.  However, it also appears, as the proposal seems to recognize, that it may be insufficient for an effective analysis.  However, the geolocation data may help resolve this.  With respect to this location data, it may be worth considering something different from using it with a population density map.  Rather, it could be used to locate the schools' census bureau tracts or "subminor civil divisions", which will then allow attaching data from the Puerto Rico Community Study (the PR version of the ACS) or the census.  This probably would give greater traction for the research goals.

Does the TETA-PR anywhere provide  scores by grade, even for PR as a whole?  The research seems to face a potential compositional problem.  If the distribution of scores varies by grades, and the distribution of students by grades differs between urban and rural, then a difference in scores by urban/rural could be magnified or suppressed by differences in the distribution of students across grades. 

Another potential issue to consider is differential attrition.  Is there a difference in the numbers or type of students dropping out of school?  This is a possible selection bias issue.
Causal Interpretations The causal interpretation offered seems well-reasoned, but it is not readily apparent how it fits the research question.  If we expect urban dwellers to do better on English because they are exposed more to the language, we would seem to be arguing that it is not a difference in schooling outcomes, but rather a spurious compositional effect.

The PRCS (as mentioned above) could help with variables to examine potential alternative causes.  Of course, if the PR Dept. of Ed. has other school level data, that would also be valuable.

At the bottom of p. 2, does the proposal need to "guess" at the residential patterns of bilingual residents - is this available this from the Puerto Rican Community Survey or other data?
Research Value The potential research value is evident, but the proposal still should address this directly in a brief paragraph, rather than just in the general opening and closing.  Remember to stress the goals of filling lacuna in the scholarly literature (such as the simple absence of information about PR) and the potential to extend existing research (as in the different language and the ethnic homogeneity).
Timetable The timetable seems okay.  As mentioned above, although learning ArcGIS is worthwhile of itself, simply identifying census locations for schools might be a better time use.
Citations & Biblio Fine.
Quality of writing Very good.
   
Priorities for Revising for Final Draft Overall, the proposal development seems to be on track.  Aside from the obvious goals of improving all parts incrementally, the revisions might stress extending the data and the causal analysis (which are interdependent).
Miscellaneous Notes The proposal draft benefits considerably from the clear writing style.  The conclusion could be more focused and shorter (the clarity of the proposal as a whole supports having a brief conclusion, unless you have something new you want to present in the conclusion).

The proposal notes that 96.7% of residents identify as Hispanic or Latino and conclude that the island is very racially homogeneous. However, doesn't the US Census currently ask the Hispanic/Latino question separately from the racial identity question?  On the racial identity question, isn't there significantly less homogeneity because there are many Puerto Ricans who identify as Hispanic & White and many who identify as Hispanic & Black?