No, not directly.
PostRFP RFX questionnaires are richly structured documents: sections can contain nested subsections, questions can contain multiple input fields, input fields can be arranged in grid-structures. This nested structure does not usefully map to the two dimensional (rows and columns) model of a spreadsheet. In fact, one of the main benefits of PostRFP is that it supports exactly those tasks which are difficult and error prone in a spreadsheet - nested structured, cascading weightings, full text answers, automatic scoring etc etc.
It is possible to download simple spreadsheets with one row per question, showing only the title. Look for "Scoring Matrix" or "Weighted Scores Report" under "Reports" in the project tree menu
It is also possible to define a complex spreadsheet which captures any combination of RFX questionnaire data - "Answer Reports"