Hi cjmc...
I'm in Madrid and hope that you get a response from someone locally in Sevilla.
I've looked around a bit for English language, flat rental sites to no avail. I found a decent Spanish language site that returned about 5 listings for the 'sevilla' area:
dirección población m² hab. baños ascensor terraza nuevo precio
zona nervion sevilla 90 3 1 - sí - 380,00 eur
c. cean bermudez sevilla 70 2 1 - sí - 540,00 eur
avda. de la aeronautica sevilla 140 4 2 sí sí - 600,00 eur
zona los remedios sevilla 105 4 1 sí sí - 800,00 eur
c. joaquin morales torres sevilla 90 3 1 sí sí - 800,00 eur
If you want to try and run some of your own searches, the site URL is:
http://www.servihabitat.com/index.jspThat may not help much but it may get you started. I would also plan to stop by a local kiosk/newsstand once you arrive as papers like '
segundamano' (I think they have that in Sevilla could be more effective than the site that I've just provided you with.)
Please let us know how it goes! B)